The main constraint of classical off-axis reflecting systems is the primary astigmatism that by long time has been a research topic of interest. This astigmatism in off-axis spherical reflective imaging systems can be eliminated by one proper configuration. These configurations could be derived from the marginal ray fan equation and they are valid for small angles of incidence. The conditions for the astigmatism compensation in configurations with two and three offaxis mirrors have been derived and analyzed, which has not been reported previously. The expression that defines the conditions for primary astigmatism compensation in a four-mirror system is presented. This shows that the marginal ray fan equation can be used to obtain the condition for astigmatism compensation of a reflective system with any number of mirrors.

The holographic gratings on photopolymer films are studied by different spatial frequency and thickness to determine the evolution of diffraction efficiency during holographic recording. The experimental results are presented like a function of energy exposure, thickness and spatial frequency. The photopolymer emulsion is prepared with potassium dichromate and nickel (II) chloride hexahydrate in polyvinyl alcohol matrix. The maximum diffraction efficiency reached is at spatial frequency (f₂) for sample A.

A design of a scatterometer is described for applications of Mie theory. The instrument comprises a goniometer, a lock-in amplifier, a laser, and a photomultiplier tube (PMT). An embedded control programmable hardware and Windows-based Virtual Instruments simplify the design of automation of the scatterometer. The software has been modularly designed to provide independent control of the stepper motor for the motion of goniometer arm, running and on-line displaying of angular scans, auto storage of the angular scan data. The obtained benefits include facilitation of advanced data-collection techniques and collection of higher quality data. Quasimonodisperse particle of the latex have been characterized with this set up. The measured size particles are close to the reported nominal values. This result indicated that the experimental setup warrants adequate quality measurement, which allows a reasonable solution to inverse problem.

The Laser-direct writing technique combined with a reflowing thermal treatment has demonstrated its capability to provide microlens array with small diameter and good focusing capabilities. In this paper we analyze the influence of the thermal treatment at temperatures of 650°C, 660°C, and 670°C, on the optical aberrations of the manufactured glass microlens arrays by ablation with a Nd:YVO₄ laser. We observed that by increasing the reflowing temperature we reduce the microlenses optical aberrations and increase the resemblance between microlenses. In particular at 670°C we obtain high quality microlens arrays characterized with a root mean square aberration of λ/28 ± λ/77, strehl ratio of 0.9475±0.0352 and depth of focus of 16.438± 5.762 μm. Our results show the reliability of the combination of the Laser-direct writing technique with thermal treatment for fabricating high quality microlens arrays.

An optical recording technique, called retardagraphy, can record a retardance pattern of a birefringent object on a polarization-sensitive medium made of azobenzene copolymer. In holography, a recording laser beam must be split into signal and reference parts. In contrast, it is not necessary for the retardagrapy to split the recording laser beam. This feature simplifies the optical system. The multi-valued phase pattern recorded on the polarization-sensitive medium can be reconstructed by measuring a retardation between two polarization components. The optical recording and reconstructing methods of binary and multi-valued phase patterns are demonstrated by retardagraphy.

Experimental results using Liquid-Crystal Variable Retarders (LCVRs) to measure the four Stokes parameters of a light beam simultaneously are presented. We use known waveplates (half-wave and quarter-wave) as known sources to provide controlled polarization states to the Stokes polarimeter, and we use the measured Stokes parameters as functions of the orientation of the axes of the waveplates as an indication of the quality of the polarimeter. The effects of errors in optical alignment and nonlinearity of the retardance variation on the results are presented and discussed. We also present results of simulations for comparison. Finally, we present the advances obtained in the development of a Mueller matrix polarimeter for use in a goniometric scatterometer.

A technique for measuring the radius of curvature of a convex optical surface is described. Its functioning is based on a lateral shearing interferometer and the observation of the collimation of a laser beam. Two interference patterns of straight fringes are obtained, and only when the fringes are parallel is the measurement considered. Since a previous calibration with a laser tracker or similar device is required it is not possible to measure surfaces with radii of curvature longer than ten meters due to dimensions of the laboratory. Details of resolution and measurement uncertainty between calibrated and noncalibrated modes of the instrument are presented.

We present the calculations of the higher order dispersion coefficients in a photonic crystal fiber. The dispersion coefficient is obtained from the calculated effective index of the fiber structure by double differentiation with respect to the wavelength (or frequency), or from the integral formula used to calculate the group index. Although both approaches are equivalent we show that they lead to totally dissimilar results, like different zero dispersion wavelength and hence the higher-order dispersion coefficients are different. In fact, the way in which the higher-order dispersion coefficients are calculated will affect the prediction of the dynamics of the supercontinuum generation. This effect will be discussed in this work.

Absolute optical thickness is a fundamental parameter for the design of optical elements. In semiconductor industry, it is necessary to measure the absolute optical thickness of the central part of the projection lenses with a high accuracy. However, even when the geometrical thickness is perfectly known, a typical refractive index of fused-silica has an ambiguity of 6 × 10^-5 that gives an uncertainty of 180 nm in the optical thickness for a 3 mm-thick plate. Moreover, the optical thickness measured by white light interferometry and wavelength tuning interferometry is an optical thickness with respect to not the ordinary refractive index but the group refractive index. We measured the ordinary optical thickness of a fused silica plate of 6-inch square and 3 mm thickness by a wavelength tuning interferometer with a tunable phase shifting technique. We assumed the typical refractive index and dispersion of the fused silica as approximate values. The absolute interference order for the optical thickness was finally estimated, which gives a measurement resolution of typically 10 nm for the optical thickness.

Stokes polarimetry using variable retardance elements such as Pockel´s cells and liquid crystals is a well-developed technique. There are two standard methods of analysis to extract the Stokes vector from the data using only one detector. One is to use only certain values of the retardances to obtain data for a number of fixed polarization combinations. The other is to use all the polarization combinations of the retardances for an oscillating voltage applied to the cells, and perform a Fourier analysis on the time varying signal. This method requires a linear relationship between the applied voltage and the obtained retardance. However, in general, for liquid-crystal variable retarders, this relationship is not linear. We present an analysis of a proposed method to use a nonlinear voltage-retardance relation to extract the Stokes parameters of a light beam. The method assumes a known nonlinear function relating the voltage and the retardance and uses a least-squares fit of the measured data to the calculated Mueller matrix of the polarimeter.

Cactus nopal dye is introduced into a polyvinyl alcohol matrix achieving a like brown appearance thick film, such that they can be used as a recording medium. This dye material provides excellent property as photosensitizer, i.e., easy handling, low cost and can be used in real time holographic recording applications. The experimental results show the diffraction efficiencies obtained by recording grating patterns induced by a He-Cd laser (442nm). For the samples, a thick film of polyvinyl alcohol and dye from cactus nopal was deposited by the gravity technique on a glass substrate. This mixture dries to form a photosensitive emulsion.

There is strong evidence that the living human retina has polarization signatures that could be linked to the presence of Glaucoma, an ocular disease that is the second cause of blindness in the western world. In a polarization sensitive ophthalmoscope, the amount of light that can be used is limited for the safety of the subject, and the return is typically a small fraction of the light used for illumination, of the order of 10^-6. Furthermore, the acquisition rates have to be sufficiently fast to avoid eye-movement artifacts. The light-budget available to produce a polarization image with a scanning laser ophthalmoscope is typically in the order of 10 nW, and pixel acquisition sampling rates are of several MHz. We are currently developing an imaging instrument for vision research and clinical vision applications and aim to introduce it to the medical and clinical environment using objective methods of image quality assessment. Here we discuss the stringent imaging requirements, polarimeter design, and show high resolution polarization retinal images.

In general, to determinate applications of liquid crystal spatial light modulators (LCSLM), it is necessary to find the display operational modulation curves, considering the optical setup in which it will be used. This requires the use of a SLM physical model to characterize the Jones matrix of the device. From these, the modulator operation curve is obtained under any polarization configuration, and it is possible to predict the SLM behavior, to modulate in amplitude or phase modulation. The characterization procedure is usually performed with normal incidence. Nevertheless, if the illumination is off-axis, it could deteriorate the prediction of their behavior and consequently the expected modulation of polarized light. In this work we analyze experimentally the behavior of the transmissive LCDSLM when the incident beam impinging on it is off-axis. It is observed that the amplitude modulation is scarcely noticeable, when the incident light beam is non-perpendicular to LCD, different to configuration 0°, as it was characterized. The situation is different when we study the phase only modulation configuration. In this case, a variation in operation curve versus inclination of incident light beam is observed. This result can be important to optimize some experiments or to take advantage, in only one optical setup, to implement polarized beams with controlled slight phase differences between them. Likewise, the Jones matrix of the LCSLM dispositive is obtained, and it is possible to observe variations in any matrix components whereas the angle of the incident light beam is varying. Also, experimental curves for amplitude and phase modulations are presented.

The paper gives an overview on 3D television which can be realized by a number of methods: stereoscopy, autostereoscopy, integral imaging, volumetric display, and digital holography where digital holograms - recorded or computed - are fed to spatial light modulators (SLM). All methods have their specific advantages and disadvantages, which can be reduced parallax, lacking motion parallax, limited lateral resolution, occlusion problem, or the severe accomodation conflict, causing eye fatigue and other discomforts. By principle holography exhibits none of these imperfections, but the problem of the necessary high space-bandwidth-product is the main obstacle for its introduction for 3D TV up to now. The needed high space-bandwidth-product requires CCDs and SLMs with higher number of pixels, a shorter pixel pitch, and faster computers than available today. Here we present first solutions to the space-bandwidth-product problem, e. g. by restricting on horizontal parallax only, by using eye-trackers resulting in calculation of only the observed small parts of the hologram, by employing image plane holography instead of Fresnel- or Fraunhofer-holography, or by using a proper combination of electrically together with optically addressable SLMs.

We present the capability of the holographic gratings implemented in photopolymerizable glasses to be applied in spatial and spectral manipulation of femtosecond laser pulses. For this purpose we used volume phase holographic gratings recorded by the interference of two monochromatic and coherent beams coming from a Nd-YAG continuous laser. We carried out experiments to determine the main features of the diffracted beams originated by the interaction of volume holographic phase grating structures with femtosecond pulses arising from the fundamental emission of an amplified Ti: sapphire laser system and its second harmonic. Meanwhile we have performed experiments to determine its damage threshold indicating that this material is an excellent candidate for intense-fields and ultrashort laser pulse applications.

In the present work we present a simple comparative analysis of the results in the optical Fourier transform profilometry which fringe projection is produced by two different methods, dynamic moiré-like patterns and Michelson interferometer. First, the Fourier transform profilometry technique is applied in the projected moiré fringe pattern onto an object surface. Then, this result is compared to the Michelson fringe pattern projection in the same method of profilometry that is applied using the same test object. We have conclude that dynamic moiré-like fringe patterns could be used with some advantages, comparatively to the results obtained by the classical Michelson fringe patterns.

It is well known that optical phenomena in metals at IR spectral region are connected with intraband optical transitions and they are analogues of direct electrical conductivity (resistance) at low frequencies. It can be suggested that in case of alternating current flux through an amorphous metallic ribbon in external magnetic field, correlation between optical and magneto-transport properties can be emerged. It must be important that the objects of the investigations are magneto-optical effects linked with diagonal components of the optical tensor unlike Kerr or Faraday effects. Experimental appearance of magneto-optical effects comprises significant changes of optical conductivity and real part of dielectric permeability via influence of external magnetic field. The magneto-transport properties depend on the effective differential permeability, on the type of domain structure and corresponding densities of electron states at the Fermi level. Optical functions of the amorphous metallic alloys ribbons of Co-Ni-B are obtained at spectral region of 1.0-5.0 eV. Changes of optical conductivity spectra of the ribbons' surface in the presence of applied external magnetic field are revealed. Variations of optical and magneto-transport properties caused by superseding of one 3d transition metal (Co) to another (Ni) are obtained. Parameters of electronic subsystem were calculated. Interconnection between electronic structure of the amorphous metallic ribbons' surface and its magneto-transport properties is established.

The Fourier transform optical systems, creating an image and/or realizing its accurate spectral characterization, suffer from appearing remarkable level of side-lobes in the image intensity distribution that reduce performances, in particular, the dynamic range of these systems. Therefore, suppressing side-lobes in the image plane represents an actual practical task being important for various scientific and technical applications such as, for example, direct imaging and spectral characterization of Earth-like extra-solar planets or spectrum analysis of ultra-high frequency radio-wave signals with exploiting an advanced acousto-optical technique. We suggest applying as apodization systems novel refractive optical beam shapers of the field mapping type, which are able to convert the input (more or less) uniform intensity distribution, peculiar to the majority of usually exploited sources of light, to arbitrary pre-scripted intensity distributions. In the case of choosing, for instance, Gaussian, cosine on a pedestal, etc. distributions, these shapers make it possible to minimize the total level of side-lobes significantly and to increase, in doing so, the dynamic range of optical data processing up to 40 dB or more. The operation principle of these beam shapers is based on inducing, in a control manner, spherical aberration in order to provide the required intensity profile transformation and further compensation of that aberration. As a result, the beam shapers operate as telescopes of special type; they produce a low divergence collimated beam with a target intensity distribution and flat wave front. We describe the beam shaper design, implementation examples, and results of practical applications to the acousto-optical technique of precise multi-channel spectrum analysis.

A Mach Zehnder (MZ) interferometer was implemented to analyze a phase object using polarization phase-shifting interferometry. The Mach Zehnder interferometer produces two beams with circular polarization of opposite rotations one respect to the other. The system is coupled to a 4-f system with phase grating in the Fourier plane, interference of the fields associated with replicated beams centered on the diffraction orders is achieved by a proper choice of the beams spacing with respect to the gratings period. The optical configuration allows obtaining n-interferograms in one shot. The configuration presented does not require micro-polarizer arrays or additional software to eliminate noise caused by vibration, as the system is stable itself and uses conventional polarizing filters. Considering the object under study a thin phase object, experimental results are presented.

In this work we present a parallel polarizing phase shifting interferometer based in a Double Cyclic Interferometer (DCSI) to analyze transparent samples. This system has the advantage of generating four beams that can interfere properly; this can reduce the number of captures needed in phase shifting interferometry. The interferometric system generates two π-shifted interferograms, which are recorded by the CCD camera in a single-shot. For the processing of the optical phase data map, a parallel phase shift can be generated by placing a linear polarizer covering two patterns. We analyze the cases of four patterns with arbitrary shifts captured in two shots. The unwrapped phase is processed by Kreis methods. Experimental results obtained by the proposed interferometer are presented.

An interferometric method to measure the slope of phase objects is presented. The analysis was performed by implementing of a polarizing phase shifting cyclic shear interferometer coupled to a grating interferometer. This system can obtain four interference patterns with adjustable phase shifts and variable lateral shear. In order to extract the slope of a phase object, is analyzed the optical phase applying the classical method of phase extraction.

Planar step-index waveguides of SiO₂:TiO₂ and ZrO₂:CeO₂ in multilayer structures were prepared onto commercial glass substrates using a sol-gel technique combined with dip-coating. These coatings were previously optically characterized by Ellipsometry. These glassy coatings were structural characterized by Transmission Electron Microscopy (TEM), Energy Dispersive X-ray analysis and Confocal Microscopy. Thicknesses of 1050 nm and 500 nm and refractive indices of 1.64 and 2.07 for SiO₂:TiO₂ (70:30) and ZrO₂:CeO₂ (70:30) waveguides were obtained, respectively, by the analysis of the guided TE and TM modes observed by Dark m-line Spectroscopy. Losses of 1.32 dB/cm and 0.86 dB/cm were respectively measured by a method based on scattered light.

The numerical reconstruction of digitally recorded holograms can be done via different approaches. Convolution, angular spectrum and Fresnel transform are the most widely used. The size of the reconstruction pixel equals that of the recording device for the two former and for the latter that size is controlled by the experimental parameters; wavelength, number of pixels and reconstruction distance determine the achievable size of the of the reconstructed pitch hence the magnification of the holographic system. It has been a challenge to have a numerical reconstruction method in which the magnification can be chosen at will. In this work, a method for numerical reconstruction of digitally recorded holograms with variable magnification is presented. It is supported on the Fresnel-Bluestein transform that allows for changing the magnification, namely the size of the reconstruction pixel, independent of distances, wavelength and number of pixels. The method is applied to reconstruct holograms recorded in off-axis and in-line setups. The reached magnification is contrasted with that achieved as the holograms are reconstructed with Fresnel transform. Since the proposed method does not modify the number of pixels of the hologram, neither the wavelength nor the reconstruction distance, it suits for application like color digital holography, metrological application among others.

We describe a hybrid technique for fabricating microlens arrays on soda-lime glass substrates composed by a direct-laser write and post thermal treatment. In particular we use a nanosecond Q-Switch Nd: YVO4 laser and a mufla Heraeus furnace. Temperature dependence of the reflowing process was analyzed in the range of 620°C-670°C. An improvement in the optical quality of the microlens arrays were obtained as temperature increases. The best microlens array was obtained at 670°C with the following characteristics: diameter 47.89±6.65μm; focal length 510±10μm; and focal spot size 2.82±0.02μm. The presented technique has been shown to be capable of fabricating low cost microlens arrays with good optical quality.

Here we present the results of theoretical and experimental determination of effective circular phase anisotropy, effective linear phase anisotropy, effective linear amplitude anisotropy and effective circular amplitude anisotropy of a composed polarization system with the properties of a quarter wave plate. It has been shown that the effective linear phase shift of such polarization system is not equal to the quarter wave plate phase shift and depends on the single wave plate parameters.

We present a polarimetry-based far-field method for high-resolution optical microscopy. The method is based on the measurement of scattering-angle-resolved polarization state distributions across the exit pupil of a high numerical aperture objective lens and allows us to distinguish between different sub-resolution objects with no need for an active scanning. Our numerical and experimental results show that the scattering-angle-resolved polarization state distributions can be used in the characterization of particles and structures with features below or at the edge of the Rayleigh resolution limit.

The application of partially coherent optical beams for imaging, free space communication, random medium analysis requires controlling its mutual intensity. This task can be done using the phase-space tomography method consisting on the reconstruction of the Wigner distribution (WD), and therefore the mutual intensity, from its projections associated with the fractional power spectra. We propose two schemes that apply spatial light modulators (SLMs) for the measurements of the required WD projections in the case of one- and two-dimensional optical signals. The use of the SLMs allows rapid data acquisition and operative change of the projection number. Moreover, the measured intensity distributions do not require further rescaling, which accelerates the WD reconstruction algorithm and improves its efficiency. The developed numerical methods provide different ways for data analysis such as the reconstruction of the WD using the inverse Radon transform and its visualization for the case of one-dimensional signals; the determination of the mutual intensity for two fixed points without previous reconstruction of the entire WD for two-dimensional signals, etc. The validity of the proposed approaches has been verified experimentally for the test signals and the results are in a good agreement with the numerical simulations.

The meter device presented in this work consists of a photo-detector mounted on the mechanism of a mobile rectangular arc. One stepper motor located on the lateral axis of the device displaces the sensor along a semi-circular trajectory of 170°, almost half meridians. Another motor located at the base of the device enables 360° rotation of the illumination source under test. This arrangement effectively produces a semi-spherical volume for the sensor to move within. The number of measurement points is determined by programming the two stepper motors. Also, the use of a single photo-sensor ensures uniformity in the measurements. The mechanical structure provides enough rigidity for supporting the accuracy required by the data acquisition circuitry based on a DSPIC. Measurement of illumination sources of different sizes is possible by using adjustable lengths of the mobile base and the ring for a maximum lamp length of 0.16 m. Because this work is partially supported by a private entity interested in the characterization of its products, especial attention has been given to the luminaries based on LED technology with divergent beams. The received power by the detector is useful to obtain the irradiance profile of the lighting source under test. The meter device presented herein is a low-cost prototype designed and fabricated using recyclable materials only such as "electronic waste".

In this paper the modificated method of calculation of fractal dimension is described. The method is based on effective averaging procedure and deals with the number of fractal generation levels. The existing methods of calculation of fractal dimension need the information about structure factor or scaling factor, which are generally unknown for real objects. The offered algorithm of calculation fractal dimensions allows to calculate fractal dimension of object with a relative error less than 1%. Thus for calculation of dimension there is no necessity to reveal the factor of structure and scaling factor. The method was checked on the wide range of two-dimensional fractals with exact self-similarity and different values of fractal dimension.

This work presents a study of lamps characterization concerning its lamp output, current and voltage drift during seasoning and regarding the use of theses lamps as luminous flux secondary standard. The 200W halogen lamps are seasoned for 30 hours and during the seasoning period the relative drift of the lamp illuminance, current and voltage are measured at each 3 minutes. The illuminance is measured using a photometer with detector head, the lamp voltage is measured using a 6.5 digits voltmeter and the current is measured using a 6.5 digits voltmeter and 0.1 Ohms standard resistor. The lamp current is controlled by a calibrated current power source with stability better than 1 mA. To reduce the stray light, baffles are positioned between the lamp and the detector head. The alignment of experimental assembly is made by a He-Ne Laser. Data of illuminance, current and voltage is acquired by software built in Labview database. Among the 5 lamps seasoned, the best result presents the variation of illuminance of 0.04% per hour. This lamp is chosen to become the secondary standard and its luminous flux is measured using an Ulbricht integrating sphere. This method allows the laboratory to create secondary standard of luminous flux for its routine test and measurements and to supply theses standards for Brazilian industry.

In this work, we present the design of a photoacoustic system to study the photoacoustic phenomena that can be used for the experimental determination of the thermal diffusivity of solids. The photoacoustic system with an open photoacoustic cell studies the photoacoustic signal of Fe₂Mo pellets that have been produced from powder by gas-solid reduction. we use the Rosencwaig and Gersho (RG) model to determine the thermal diffusivity of Fe₂ Mo. The thermal diffusivity of the Fe₂Mo calculated is 0.0147 cm²/s ± 0.0001.

Residual stress of as-deposited coatings may cause bending of the coating/substrate system. If residual stresses are present and the overall deflection is small compared with the substrate thickness, then by symmetry the coated substrate will take up a spherical curvature in the region away from the edges. Near the edges a complex stress state will be present. However away from the edges this reverts to a simple stress state where stresses normal to the substrate and shear stresses are zero The three-dimensional inspection of thin films deposited in thin substrates allows the assessment of film's residual stress. In this communication we report on the use of this method illustrating it by performing the residual stress evaluation PVD onto glass deposited thin films using optical non-destructive and non-invasive microtopographic inspection using an active optical triangulation sensor developed by the first author at the Universidade do Minho. It allows depth measures with resolutions down to 2nm and lateral resolutions down to 1μm. The three dimensional map and corresponding coordinate set obtained allow the calculation of the stress distribution over the film.

A few optically matched by each other sub-systems related to an advanced prototype of acousto-optical spectrometer for radio-astronomy are analyzed jointly. Rather precise control over the incident light polarization should be assured in the scheme together with a required expanding of the incident light beam. Moreover, the needed light-beam apodization, suppressing side lobes within registration of each individual resolvable spot and increasing the dynamic range of spectrometer, has to be taken into account as well. The current stage of analysis related to afore-mentioned problems as well as the results of trial experiments are presented.

The astigmatism in reflective imaging systems can be eliminated by a proper configuration. However, the spherical and coma are the main residual aberrations in third order theory, but the behavior of all aberrations is not yet fully The main aberration of classical off-axis reflecting systems is primary astigmatism. The astigmatism in off-axis spherical understood. Expressions for the wavefront aberrations in an off-axis spherical mirror are presented. These formulas are derived from the optical path difference between an ellipsoid and a sphere, assuming a relatively small pupil and a small angle of incidence as it will be described with detail. Using the principle of the optical path difference, we developed the mathematical expressions that describe the third order wavefront aberrations in a two spherical mirror system when the object is finite.

We report the characterization and analysis of photochromic films gallus gallus albumin as a matrix modified for holographic recording. Photo-oxidation of homogeneous mixtures prepared with albumin-propylene glycol, to combine chemically with aqueous solution of ammonium dichromate at certain concentrations. We analyzed the diffraction gratings, through the diffraction efficiency of the proposed material. Also, eosin was used as a fluorescent agent, so it is found that produces an inhibitory effect, thus decreasing the diffraction efficiency of the matrices prepared in near-identical circumstances. The work was to achieve stability of albumin films, were prepared with propylene glycol. Finally, experimental studies were performed with films when subjected to aqueous solution of eosin (fluorescent agent) to verify the ability to increase or decrease in diffraction efficiency.

In this work we present a different method to reduce shot noise in phase imaging from digital holograms. An averaging process of phase images reconstructed with different reconstruction algorithms of the complex amplitude of a phase object in digital holographic microscopy. We obtain an improved phase image reaching a 29% of shot noise reduction. We use a single object complex amplitude that is needed to perform our proposal. Also show the corresponding simulations and experimental results. As phase sample test we used a micro-thin film step surface made at home of 100 nm high of TiO₂ on a glass substrate of 4.7 mm thickness, our system was calibrated and traceable to an Atomic Force Microscope results.

It is well known that the Ronchi test can be used to measure the derivative of the optical path difference of a wavefront [1]. Therefore when the Ronchi test is used to determine the wavefront of the surface under test, two orthogonal Ronchigrams are required to reconstruct the surface [2]. We present a simple method to recovery the wavefront with one Ronchigram without using polynomial fit or trapezoidal integration. The recovery of the aberration coefficients of third order is achieved by assigning random values but controlled in the equation of the optical path difference (OPD) which is given for a lateral sheared interferometer. Since the Ronchi test can be seen as a variation of this type of interferometer [3], namely, the OPD for the Ronchi test is given by the difference between the original wavefront W(x,y) and the sheared wavefront W(x + Δx,y), resulting in the generation of various Ronchigrams, which are compared with the Ronchigram under analysis. The generated Ronchigram with lower RMS (Root Mean Square) must have the highest correlation with the Ronchigram analyzed, since the RMS is inversely proportional to the correlation. For some simulated Ronchigrams which were generated by introducing Gaussian noise, some results are shown. The proposed method retrieves in a reliable the coefficients of the polynomial of the analyzed Ronchigram in a reliable and accurate way.

We describe a simple and precise experimental procedure for the detection of the transverse fluorescence emitted by excited ions in erbium-doped fibers. The modulation of the optical pump (980 nm) power allows distinguishing between transverse fluorescence and pump radiated modes in the measured optical signal using a broadband InGaAs detector.

Precision machining is as a very precise and effective method for micro-structure optical components fabrication. In this paper, the mechanical structure of one XYZ and spindle axis of freedom machine with 250 nm of resolution in linear axes is described, details of the homemade mechanical mounts are given; also components of the electronic system such as hardware, firmware and software are included in the description.

We developed an automated system in micro and optical fiber fusion, using stepper motors of 3.6 ° (1.8 ° Medium step) with a threaded system for displacements in the order of microns, a LM016 LCD for User message management, a PIC16F877A microcontroller to control the prototype. We also used internal modules: TMR0, EEPROM, PWM (pulse width modulation) control using a pulse opto-cupped the discharge circuit high voltage (20 to 35 kilovolt transformer for FLYBACK fusion) The USART (Universal Synchronous Asynchronous Receiver Transmitter) for serial interface with the PC. The software platform developed under Visual Basic 6.0, which lets you manipulate the prototype from the PC. The entire program is optimized for microcontroller interrupt, macro-functions and is written in MPLAB 7.31. The prototype is now finished.

Based on 30 years of optical testing experience, I have defined seven guiding principles for optical testing. This paper introduces these rules and discusses examples of their application.

Parametric cost models are used to plan missions, compare concepts and justify technology investments. This paper reviews an on-going effort to develop cost modes for space telescopes. This paper summarizes the methodology used to develop cost models and documents how changes to the database have changed previously published preliminary cost models. While the cost models are evolving, the previously published findings remain valid: it costs less per square meter of collecting aperture to build a large telescope than a small telescope; technology development as a function of time reduces cost; and lower areal density telescopes cost more than more massive telescopes.

In this work we present an efficient proposal to evaluate optical surfaces working at infrared wavelengths based on the Ronchi test and on the concept of synthetic wavelength. The implementation is performed by using a spatial modulator (XGA2 SLM) and a white Light Emitting Diode (LED) of 5mm. In order to select distinct wavelengths, different color filters are employed. Thus, for a given selected wavelength, the surface evaluation is carried out according to the method of Ronchi, registering two perpendicular interferograms for this color; the process is repeated for a second wavelength (architecture of this proposal allowed us to test the surface in more than two wavelengths). Then, an equivalent ronchigram is computationally generated with the registered data which is then analyzed in order to generate the wavefront for the correspondent synthetic wavelength. Observations of our results show that with an appropriate LED alignment and high intensity, we avoid an increase of noise due to the employment of longer wavelengths, as well as the alignment problem, often linked to the evaluation of infrared (IR) surfaces. The simplicity of the optical setup and low cost materials make this proposal applicable in the area of optical testing.

Digital In-line Holographic Microscopy (DIHM) is a two-steps microscopy technique that allows for accessing to complex wave information of the optical field scattered by a sample. Initially, the sample is illuminated by a spherical wavefront such that the amplitude superposition of the portions of the spherical wavefront scattered and not by sample, is recorded on a digital camera; the recorded intensity is often referred as in-line hologram. On the second step, a numerical diffraction scheme is used to emulate the diffraction of a spherical wavefront by the in-line hologram therefore producing a reconstruction in amplitude and phase of the original object. Due to its evident experimental simplicity, DIHM is a widely used technique for in-situ applications and more recently on real time measurements. This widespread employment of the technique introduces the necessity of establishing the practical limits achievable with this imaging technique. Particularly, for the practical study of mono-disperse colloids, the critical concentration is a relevant factor to identify, in order to establish the optimal conditions up to which DIHM can successfully work. The reconstruction step produces a set of intensity images, at different axial distances, containing the information of all the recorded particles; in large study volumes and high concentrations the number of particles overcome the easiness of manual processing and therefore evidences the need of implementing more automatic tracking algorithms. In this way the limits of applicability of DIHM rely on both the experimental configuration and the digital processing. With the use of a modeling tool for DIHM and a semi-automatic tracking algorithm, a numerical estimation of the concentration limit for which DIHM can work is proposed, following the analysis for its dependence with the experimental configuration of the recording process.

Today's room temperature microbolometers focal plane arrays are the most widespread technology for the registration of thermal images. Other attempts to develop detection systems are based on the idea of converting the thermal information into visible. Thermal to visible converters try to achieve the possibility of "detecting" thermal radiation with common visible detectors. The development of these converters may provide IR and thermal detection methods for specific thermal imaging applications without excessive investment. Previously, we have proposed a conversion method based on temperature dependence of the fluorescence emission of a europium-doped complex. Here, we present the analysis of the temporal response of the sensing element and we also specify the desirable thermal and physical characteristics of such element in order to allow thermal to visible conversion in real time. With the analysis of the frequency response of the EuTTA fluorescence, we find that the emission presents a response that allows dynamic conversion. Furthermore, we analyze the thermal-transient response of the sensing element of the converter. Based on heat transfer simulation of a pixel of the sensing element, we establish the characteristics that the thermal design should fulfill in order to have efficient heat transfer in a dynamic converter.

A new design of a null Hartman's screen to test quantitatively a fast plano-convex conic lens is presented. The design of the null screen is based on the caustic produced by refraction through the lens. Additionally, the null screen can be used to improve the alignment in optical systems. A quantitative evaluation of medium precision by using a trapezoidal integration method is presented.

We derive simple formulas for the caustic produced by a positive convex-plano and plano-convex conic lens by considering a plane wave incident on the lens along the optical axis. By using these equations a paraxial approximation for the caustics are provided in both configurations. Also, by using these equations it is possible to obtain the third order coefficient of spherical aberration. Changing the parameters of the lens (refraction index, conic constant, radius of curvature, thickness of the lens, etc.) we can modify the shape of the caustic, furthermore there are cases where the spherical aberration changes from positive to negative when we vary exclusively the conic constant. A formula for the Principal Surface as a function of the height also is given. We believe that the method to obtain the caustic that we report is straightforward, obtaining a relationship between caustics, wavefronts, and measurements of the spherical aberrations.

This paper presents the opto-mechanical design of a novel spectroscopic element - sliced pupil grating - that allows increasing the spectral resolution while keeping the instrument geometry. The concept is based on "cutting" the pupil into different slices by placing a number of prisms at the two sites of a VPH grating. The independent beams are guided through a precise opto-mechanical assembly to assure the recombination of the individual images on the detector within the available error budget, producing a single spectrum. To probe the feasibility of the concept, we have designed and manufactured a 3-slice prototype for an already-built spectrograph (Elmer, for the GTC 10-m telescope).

The purpose of this work is to describe some optical and mechanical issues relating to the fabrication of the camera and the collimator of the Equalized and Diffraction-Limited Field Spectrograph Experiment (EDiFiSE), an instrument which forms part of a bigger project of the Instituto de Astrofísica de Canarias (IAC), Spain, and that was designed and manufactured within the facilities of Centro de Investigaciones en Óptica in León, México.

We describe an analytic formulation that describes the spatial behavior and propagation of a class of fully correlated beams that span the complete Poincaré sphere. The beams can be constructed from a superposition of a fundamental Gaussian mode and a spiral phase Laguerre-Gauss (LG) mode having orthogonal polarization. When the orthogonal polarizations are right and left circular, the coverage extends from one pole of the sphere to the other in such a way that concentric circles on the beam map onto parallels on the Poincaré sphere and radial lines map onto meridians. If the beam waists match, the beam propagation corresponds to a rigid rotation about the pole; a mismatch in beam waist size or position produces a beam in which parallels rotate at different rates with propagation distance. We describe an experimental example of how a symmetrically stressed window can produce these beams and show that the predicted rotation indeed occurs when moving through the focus of a paraxial Gaussian beam. We discuss nonparaxial behavior and end with a discussion of how the idea can be extended to include beams that not only cover the surface of the Poincaré sphere, but fill the volume within the sphere.

The design of diffractive optical elements (DOEs) to generate a desired light intensity distribution has been studied in the realm of diffractive optics. Within the proposed algorithms to perform the design and optimization of DOEs are the iterative Fourier transform algorithms (IFTAs). In this work we are interested in generating a spot array using an IFTA. We propose a modified error-reduction IFTA which allows us to reach a target error with high effciency.

By annealing thin hydrogenated amorphous silicon carbide (a-SiCx:H) films deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) on crystalline silicon (c-Si) wafers, pn-junctions with very low inverse saturation current can be formed. This has been shown in heterojunction bipolar transistors and solar cells with +/- 400°C for this process. The characterization of these structures indicates that a-SiCx:H films partially re-crystallize during the annealing process forming Si-nanocrystals embedded in the amorphous film. Understanding this process and further improving the pn-junction the study of the re-crystallization process by X-Ray Diffraction (XRD) measurements has been done. This paper deals with the characterization of amorphous SiCx/c-Si structures with 100 and 300 nm thickness measured by XRD with the temperature chamber with an annealing process at 900°C. Both intrinsic and phosphorus-doped a-SiCx:H films were deposited on a c-Si substrate p-type of 300um-thickness with crystallographic orientation <100> using the PECVD reactor. From the in-situ measurements using the XDR, the crystallization phase was obtained; this was done by taking the maximum value of intensity at the dominant peak in the orientation <111> and normalization. Fitting this with the Avrami-Mehl-Johnson Theory the incubation as well as the crystallization time were obtained to study the thermally activated process.

Single particle position calculation in three dimensions (3D) with high accuracy is the very important in several branches of science. On the other hand, the use of in-line holography to study very small objects in a dynamic volume is a technique of importance for scientists and engineers across a variety of disciplines for obtaining information about size, shape, trajectory and velocity of small objects such as dust particles. However, in general for in-line holography, accurate determination of the object's position in the optical axis direction is difficult. In order to overcome this shortcoming, we proposed to use in-line holography set up to record particle images in two orthogonal forward configurations. In this study, we avoid digital holography reconstruction to calculate particle position. To determine particle position, the proposed method is based on the calculation of the size and position of the central spot size (CSS) of a particle diffraction image. The size of the CSS is calculated by using the Continuous Wavelet Transform (CWT) and Continuous Hough Transforms (CHT), an then the size of the CSS is related to a calibration curve calculated experimentally in order to determine the "z" particle position and centroid of the CSS render the "x-y" position of a particle image. The procedure proposed in this work to determine the 3D particle position is so simple since it avoids a complicated experimental set-up and several computational steps in order to obtain the 3D position of the particles. Our approach offers the following advantages: First, the mathematical accuracy, light illumination as well as particle and medium refractive indexes are used during the analysis. Second, it is not required to resolve the size of particle since we calculate only the size of CSS of a diffraction particle image pattern.

Tunable liquid-filled lens (TLFL) is a lens that changing their focal length by modify the quantity of liquid within the mount. Recent research shows that, the use of tunables lens makes lighter, simpler and more compact optical devices in micro-ingineering. In the literature there are papers that present simulations of the behavior of tunable micro-lenses composed slim membranes. We use a TLFL composed a cylindrical metallic mount with a compartment for two transparent elastic membranes filled with water between them. Membranes with plane, spherical and conic surfaces are employed. The membranes are elaborated of Polydimethilsolixane and the mechanical mount is made of alluminium. In this work, we present the opto-mechanical design, analysis and simulations of behavior de tunable liquid-filled lenses composed thick membranes. The analysis is made in three TLFL with different types membranes. The simulations and analysis of mechanical behavior were made with SolidWork™ software. Moreover an application with genetic algorithms was development to obtain the geometrical parameters of the lenses when a value of pressure is applied on the membrane surfaces. On the order hand, the analysis of optical behavior of the lenses was made with the OSLO software. Finaly, results are shown.

This paper shows the qualitative and quantitative results obtained on the test of cylindrical parabolic concentrators when the screens are designed using dot color changes to guarantee a better dot correspondence assignment and to make the optical test of the concentrator easier; the method allows to measure deformations from tenths of a millimeter to several millimeters, thus demonstrating that null screen method is good enough for testing surfaces with important deformations. On a second approximation, it is designed a null screen corresponding to the surface evaluated with the first one by fitting a fourth grade polynomial with crossed terms; with this, it is shown that the first test gets closer to the shape of the surface validating it.

In previous works Korneev, et al. and Cornejo, et. al. Shown the feasibility to produce an interference pattern, by setting near by the focal point of a lens a razor knife edge. The interference phenomena is produced between the wavefront coming from the lens, and the wavefront produced by the knife edge. In this work, such technique is applied for testing a lens. Since partial interferograms are observed, due to the obstruction of the knife edge to the wavefront coming from the lens; by rotation of the knife edge in several directions, interferograms with different information can be registered by means of a CCD connected to a PC. Experimental measurements are given after several interferograms with different number of fringes were analyzed.

The article presents original design and fabrication principles and main characteristics of compact 8-m resolution multiband imager for small satellite. For estimation and obtainment of maximum possible parameters of the imager in spatial resolution and image quality with strict limits of weight and dimensions of imager a complex mathematical model of imager was developed and applied, which includes and binds image quality, geometric, energy and probability factor of spatial resolution of the whole section object-atmosphere-objective-CCD array.

The wavelength of the electromagnetic radiation plays a key role on determining the spatial resolution an imaging system can achieve, the way how the wave interacts with matter and how it propagates. For this reason the measurement of the wavelength associated with electromagnetic radiation of any order is fundamental. For light, simple diffractioninterference experiments can lead to an appropriate measurement of this feature. For electrons, however, the wavelength value is calculated simply by the knowledge of the accelerating potential. In this work, we present an iterative method for measuring the wavelength of electromagnetic radiation of any order. By using the self-imaging effect that arises as an electromagnetic wave impinges on a periodic object, the wavelength of the wave can be determined. Experimental results of the application of the method to measure the wavelength of light are shown. The basis for the application of the method to determine the wavelength of electron waves are settled.

We present the characterization of a boron doped hydrogenated amorphous silicon (a-Si:H) thermosensor bolometer array for far infrared detection. The array was fabricated over a silicon wafer on a 0.4 μm silicon-nitride (Si₃N₄) layer. Wet bulk micromachining was used to create pixels of suspended nitride film by removing the silicon underneath. On this film, a boron doped a-Si:H layer was deposited using a low frequency PECVD system at 540 K. Conventional lithography was used to define the bolometers on the nitride windows, and the 5 × 5 microbolometer array was fabricated and characterized at 77 K. A 1.17 x 10^-2 mA/W responsivity, with a temperature coefficient of resistance (TCR) of 4.25%, were obtained.

The self assembled monolayers (SAM) have become in the most popular strategy for design and generate surfaces characterizing by specific functional organic groups. The aimed of this work is applied this SAM as optical transducer in biosensors. The techniques, Infrared (in ATR mode) and UV/Vis spectroscopy have been used to study the films generated in each step in the self assembled process. The SAM was generated as follow; first silane group was added to the glass substrate. After that, the substrates were immersed in a solution containing carbomiide group (EDC). Finally the spiropyran 1',3'-Dihydro-8-methoxy-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-(2H)-indole] was attached to functionalized slides. In each process absorbance was analyzed by UV/Vis (270 to 500 nm) and FTIR (650 to 1800 cm^-1). In UV, the spectra shows an absorbance band centered at 280 associated to EDC film and a lower intensity band centered at 380 nm associated to spiropyran. In FTIR spectra, the Si-Si and Si-O bond are present below the 1250 cm^-1. The EDC film shows very weak bands in the region from 1300 to 1800 cm-1. For the spiropyran film the band associated to the C-N, N-O, C=C, C-H and aromatic ring have a very well defined peaks. Once the transducer bands were detected, it was immersed in glucose solution; the infrared spectral show bands are associated to glucose in the transducer.

In this work, we describe a phase shift interferometric monitoring of polishing processes produced by a petal tool over a spherical surface to obtain a parabolic surface. In the process, we used a commercial polishing machine; the purpose of this work is to have control of polishing time. To achieve this analysis, we used a Fizeau interferometer of ZYGO Company for optical shop testing, and the Durango software from Diffraction International Company. For data acquisition, simulation and evaluation of optical surfaces, we start polishing process with a spherical surface with 15.46 cm of diameter; a 59.9 cm of radius curvature and, with f/# 1.9.

Structured light fields, defined as laser beams which amplitude and phase distributions have been shaped to take physical forms with a high degree of complexity, are of great interest in several areas in optics due to their wide variety of applications. Such fields, in order to maintain their properties, must be generated in the most efficient and accurate way possible. Phase synthetic holograms (PSH) implemented on liquid crystal spatial light modulators (LC-SLM), have proved to be a powerful method to generate structured light fields. In this work we use six different holographic codes that we consider the most representative found in literature, to numerically evaluate their performance when parabolic beams (PBs) are encoded. Also, we present some experimental results that are obtained when the holograms are implemented on a liquid crystal spatial light modulator.

Here we report on the application of the well known photo-goniometric method, based on illuminance spatial distribution direct measurements, to determine the total luminous flux for high-intensity white LED sources; thus testing the CENAM primary metrology capabilities recently developed to face the increasing needs claimed by the rapidly moving solid-state lighting industrial sector in Mexico. These first results obtained at CENAM after the gonio-photometric method implementation, allowed us to determine in good accuracy the total luminous flux for a high intensity white LED source, with an estimated uncertainty of 2.86 % (k=1); still lower than the claimed by the tested LED manufacturer. We clearly identified the spectral mismatch correction factor determination and the LED junction temperature measurement and control as the dominant uncertainly sources, and will be addressed in order to improve the accuracy of the measurement system for future experiments.

Schottky diodes have been made on both n-type and p-type virgin mono-crystalline silicon processed by three kinds of pulsed lasers currently used in new photovoltaic technologies. The electrical characteristics of these diodes have been measured as a function of laser fluence. A strong change in all of their electrical parameters occurs for fluence equal or higher than a threshold at which the processed silicon surface layer turns into melt. Capacitance versus voltage measurements and DLTS analyses show that laser irradiations introduce a large density of deep levels related to active defects in the processed surface and bulk area. These defects are believed mostly generated during the fast quenching rate in pulsed laser treatments.

In this work we report on a fabrication method for producing large-area multilayer polymer membranes and describe its application to the instrumentation of a deformable mirror. This implementation allows for highly flexible mirrors in which mechanical properties vary in a controlled manner in order to better match optical requirements. In addition, the mechanical properties of such membranes allow for a large number of closely spaced actuators. We report on the mechanical properties of metal-polymer membranes and discuss their application to pulse shaping experiments.

In this work we present an experimental proposal for an efficient optical pressure sensor based on a Variable Liquid Lens (VLL) and a modified Point Diffraction Interferometer (PDI). The working principle of the proposed sensor relies on the fact that a pressure variation induces a change in the lens curvature and hence in its focal length which can be tracked and measured with the interferometer. The pressure is then measured by recording and processing the interferometric images. The calibration of the sensor in this proposal demonstrated a working range of 0-26 kPa with an accuracy of less than 0.1 kPa in the whole range.

The null-screen method has been used to test aspheric surfaces. This geometrical method measures the slope of the test surface and by a numerical integration procedure the shape of the test surface can be obtained. Now, in order to test the surfaces of a variable focal length lens (VFLL), we propose use a conical null-screen. We present the formulae to design the null-screen in such a way that the image on the CCD is a perfect array of spots; departures from this geometry are observed as deformation of the surface. The VFLL is designed in such a way that under conditions of mechanical equilibrium both surfaces are spherical; however, its shape can be easily modified mechanically changing its radius of curvature. In order to analyze the shape of the surfaces of the VFLL at different radius of curvature, we evaluate its form using a conical null-screen. This procedure allows study the deformations of the surface.

In this work we report the design of a null screen for corneal topography. Here we assume that the corneal surface is an ellipsoid with a diameter of 12 mm and a curvature radius of 7.8 mm. To avoid the difficulties in the alignment of the test system due to the face contour (eyebrows, nose, or eyelids), we design a conical null-screen with spots (similar to ellipses) drawn on it in such a way that its image, which is formed by reflection on the test surface, becomes an exact radial array of circular spots if the surface is perfect. Additionally, we performed a numerical simulation introducing Gaussian random errors in the coordinates of the centroids of the spots on the image plane, and in the coordinates of the sources (spots on the null-screen) in order to obtain the conical null-screen that reduces the error in the evaluation of the topography.

The null screen is a geometric method that allows the testing of fast aspherical surfaces, this method measured the local slope at the surface and by numerical integration the shape of the surface is measured. The usual technique for the numerical evaluation of the surface is the trapezoidal rule, is well-known fact that the truncation error increases with the second power of the spacing between spots of the integration path. Those paths are constructed following spots reflected on the surface and starting in an initial select spot. To reduce the numerical errors in this work we propose the use of the Dijkstra algorithm.1 This algorithm can find the shortest path from one spot (or vertex) to another spot in a weighted connex graph. Using a modification of the algorithm it is possible to find the minimal path from one select spot to all others ones. This automates and simplifies the integration process in the test with null screens. In this work is shown the efficient proposed evaluating a previously surface with a traditional process.

It is well known that astigmatic surfaces are obtained when surfaces are polished in commercial polishing machines, which are designed to produce surfaces of revolution. The authors of this paper do not know an explanation for this result. In order to understand why the wear is a function of the angular position on the glass, we measured the dragging force applied from a rotating glass to a small fixed tool of Teflon®. These experiments were done for several tool radial positions by using a table travel X-Y. With the aid of a force sensor dragging force as a function of the time was measured. We found that dragging force is a periodic function with fundamental frequency equal to the angular velocity of the glass, indicating that there is more wear on one glass angular position than another. We also found that this result is independent of the radial position of the tool. We used a polisher concentration of 20 degrees Baumé which is recommended by the supplier. And the amount of polisher per time and area units, dragged by the tool, remained constant for each one of the radial positions of the tool.

To estimate qualitatively the surface errors with Ronchi test, the experimental and simulated ronchigrams are compared. Recently surface errors have been obtained quantitatively matching the intersection point coordinates of ronchigrama fringes with x-axis . In this case, gaussian fit must be done for each fringe, and interference orders are used in Malacara algorithm for the simulations. In order to evaluate surface errors, we added an error function in simulations, described with cubic splines, to the sagitta function of the ideal surface. We used the vectorial transversal aberration formula and a ruling with cosinusoidal transmittance, because these rulings reproduce better experimental ronchigram fringe profiles. Several error functions are tried until the whole experimental ronchigrama image is reproduced. The optimization process was done using genetic algorithms.

A new method for phase-shifting interferometry based on the wave amplitude modulation is proposed and discussed. This proposal is based on the interference of three waves, where two waves attend as two reference waves and the other wave attends as a probe wave. Whereby, three interference terms are obtained, but because of a phase difference of π/2 between the two references is kept constant, one of the three terms will be dropped while the two remaining will be put in quadrature. Under these conditions the resulting pattern is mathematically modeled by an interferogram of two waves, where an additional phase is given by the amplitude variations of the reference waves. In this paper, both a theoretical model and some numerical simulations are presented

In this paper, we propose to use a Ronchi rule on a Nodal Bench to test convergent optics system. The Ronchi rule is of frequency medium, between 200 and 500 lines/inches. Besides, this test takes advantage to measure nodal plane and focal distance on-axis and off-axis of some system optics with Nodal Bench. The optics system under test is illuminated with a plane wavefront and it is focused to focal distance of the optics system under test. Ronchi rule is placed in exit pupil of optics system, it generate interferograms with the aberrations of optics system. In this interferograms we observe fines fringes of interference which are generated by the rule frequency like the rule works as a reflections multiples interferometer. The interferograms are displayed on a computer by a CCD, it is placed on the focal point of the system under test. We show some preliminary results of this test.

The design and construction of a compact instrument that automatically measures Kerr-based third order nonlinearities (both nonlinear refractive index: γ, and nonlinear absorption: β) in materials, is presented. The instrument includes control of the polarization state of the input laser beam and was calibrated with well known reference samples. The mechanical translation system and the polarizer rotation-stage are controlled via a home-made electronic circuit, whereas the data acquisition from three photodiodes is performed by a National Instruments 12-bits DAQ. The entire system is fully controlled by means of an application program encoded in LabView. The importance of the developed experimental device is its reliability, compactness, easy implementation and transport, table-top installation, low cost and high accuracy.

Off-axis parabolic elements have found application in Tera-Hertz imaging and new application in two-photon microscopy scan engines. Both these applications demand spatial and temporal precision in photon location. This modelling work examines how close off-axis parabolic elements are to the perfect image relay by calculating the geometrical performance metrics of spot diagrams, point spread functions and wavefront distortion for different arrangements of off-axis parabolas and a parabolic torus when compared to a close-coupled two mirror scan engine. Results identify the off-axis parabolic elements as a superior scan engine particularly in wide-field scan instruments. When within the optimum beam size versus parabola focus length ratio, the imaging of these systems is superb.

MEGARA is a multi-object spectrograph project for the 10.4m Gran Telescopio Canarias with medium to high resolution: R ~ 5600 - 17000. The instrument operates in three modes that cover different sky areas and that can run simultaneously: (1) the compact mode through a large central Integral Field Unit with minimum fiber pitch, covering a field of view on sky of 12 arcsec × 14 arcsec, (2) the sparse mode with fibers covering 1 arcmin × 1arcmin in three pointings and (3) the dispersed mode with a grid of nearly 100 robotics positioners able to place 7-fiber minibundles over a large field of view of 3.5 arcmin × 3.5 arcmin. The spectrograph is composed by a pseudo-slit, where the fibers are placed simulating a long slit; a slit shutter is placed just behind the pseudo-slit, a collimator, a 162mm pupil where the volume phase holographic gratings are placed, and the camera with the detector. Here we describe the spectrograph optical rationale, the conceptual optical design and the expected system performance.

It has been prototyped the basic optics and electronics of a crossed Czerny-Turner spectrograph to work at different wavelengths. The optical system of the spectrograph prototype has been simulated using OSLO software in order to optimize the capture of the light spectrum. The study that is presented in this paper is based on the optimization of the focusing optics orientation that would obtain the smallest y-spot width onto a linear CCD, for different central wavelengths. It has been changed the orientation of the focusing optics trough the simulation, and changes in the spot diagram has been observed and plotted. Finally, we have obtained recommendations using these results, how to adjust the focusing optics in real spectrographs for different central wavelengths. Simulated spectrograph had about 0.25 nm mean resolution with a focusing optics of 100 mm focal length.

The new type of diffraction fractal elements is presented and optical fields properties, obtained from these elements are discussed. Fractal diffraction elements based on well-known fractals, possess exact or statistical selfsimilarity, but have managed amplitude transmittance and phase shift, which are correlated with fractal spatial characteristics. The fractal dimension is not enough for these objects description, and the correlation coefficient between phase/amplitude and spatial characteristic is needed. For this reason the fractal objects were called multifractal structures (MFS). It is shown that the MFS diffraction spectrum possess prevailing power of high frequencies in comparison with spectra of regular two-dimensional or fractal structures with binary transmittance and phase shift. This property could be applied for spatial filtering and transparent objects phase heterogeneities detection. Modeling results for different MFS types are presented and it is shown that MFS application allows detecting the value of initial object distortion with high accuracy. The description of fractal zone plates (FraZP) with variable transmittance and/or phase shift is also presented. The results of Fresnel diffraction modeling from FraZPs with MFS show that the correlation coefficient value has influence on the focal point position.

To measure the wavefront aberrations of human eyes, a Shack-Hartmann Sensor (SHS) was developed at UNAM-CCADET. Usually, for calibrating the SHS a well corrected collimated beam is used, so the evaluation of the aberrations depends on this calibration. We propose to use a Point Diffraction Interferometer (PDI) in parallel with the SHS, in order to be able to check for aberrations in the calibration beam at any time. This allows reducing the delay between the calibration and measurement of the aberrations of the eye made with the SHS. In addition, both measurements are made without moving components, so the evaluation made through the SHS can be compensated with the reference beam measurement made by the PDI. The results of the quantitative evaluation of the wavefront aberrations of a human eye are presented in this paper.

There is increasing interest to detect extrasolar planets directly. In the last years, more than 500 planets have been discovered by means of indirect methods. However, the small signal-to-noise ratio and the small angular separation of the star-planet system have hindered the direct detection of the optical / IR signals caused by the planets. Several methods have been proposed to cancel the star irradiance and detecting the presence of the planet around them. One proposal is the rotational shearing interferometer (RSI). Previously, by exact ray trace, we determined the positioning tolerances and the resolution of the fine mirror movements needed to satisfy a maximum wavefront deviation of λ/10 (at 633 nm) in the RSI. In this work, we show a method to quantify, employing exact ray trace and the interference pattern, the critical parameters for this RSI to detect extrasolar planets.

Optical discs are widely used for storage of archival data represented in a digital form. Long-term storage of information recorded on standard CDs is provided by periodical rewriting (once in 3-5 years) on the new carriers. High-stable lightsensitive materials and special reflective metal coatings are proposed to use for increasing the information storage terms of the optical discs. The conducted researches have showed that the application of vitreous chalcogenide semiconductors in optical WORM discs assures the data storage terms up to 30 years. Substantially larger terms of data storage can be realized on the optical ROM carriers. Attainment of the guaranteed data storage terms within several hundreds years is provided in such carriers by applying high-stable materials substrates and information should be represented in the form of a micro-relief structure on the substrate surface. Sapphire, quartz, silicon, glass-ceramics and other materials can be utilized for manufacturing substrates of optical BD discs (and other subsequent high-density disc formats). These materials allow creating substrates characterized with increased melting temperature, chemical and mechanical resistance. Furthermore, using the mentioned materials for substrates production permits applying high temperature materials, such as chrome and nickel, to creation of high-stable refractive layers and demonstrating the sufficient mechanical adhesion between the refractive layer and the substrate. Modern methods of thermo-lithography offers creating of nano-size images on photo-resist layer deposited on the substrates. Those images can be transformed to the nano-size relief structures on the surface of the high-stable materials substrates by techniques of reactive ion-beam etching.

It is generally accepted that mirage is formed when temperature of the ground surface, in a flat area like desert, is higher than the temperatures of the over ground air layers. In this case, light emerging from a distant object makes total internal reflection in the air layers and forms the image of the object that is called mirage. Our investigation on mirage formation in desert indicates that there is no meaningful relation between mirage formation and temperature change over the ground. In addition, we show that, the interference of the lights reflected from different air layers destroys the coherency of the image forming light. This happens because the temperature change occurs in an interval larger than a wavelength. In the second part of the report we demonstrate theoretically and experimentally that flat rough surfaces behave like mirrors at very large incident angles. We show that there is a threshold incident angle for observation of image in a rough surface that depends on the surface roughness and light wavelength. The shortest distance between observer and the image is determined by the threshold incident angle. Mirage is such an image. Image formation is studied in rough sheet glass surfaces that prepared by grinding with powders of different sizes.

Image-plane technique can overcome the annoying "picket-fence" effect encountered in the traditional multiplex holography. Previously, we have adopted a three-step process to fabricate a reflection-type image-plane alcove hologram. Here, we design an anamorphic optical system for the object wave which is mixed with light diffracted from a line segment on a diffuser to simplify the recording process to one step. Experimental result shows single-colored image reconstructed with white light from LED. Qualitative description of some characteristics of the reconstructed image is also presented.

The fluorescent multilayer disc (FMD) consists of a substrate and the sandwich-structure of information and intermediate layers. While all the structure of the disc is transparent and homogeneous the parasitic signal will be caused mostly by photoluminescence (PL) and absorption of pits areas where laser light is unfocused. At large number of layers (10 or more) the noise level will get significant value, so it was suggested to derive readout signal as a variable one. Also it was proposed to record information only by the lands, to decrease the absorbance level and thus uncontrolled changing of the noise level. Furthermore in the FMD information layer there are inner and outside peripheral areas which hold a stable level of parasitic signal during readout from the edges of the disc. While the PL readout signal is spatially isotropic the optical head of the FMD drive receives just a part of the probing beam energy. PL quantum yield, absorption factor, receiver systems exposure loss coefficients are other reasons of the low PL signal. Thus the problem of the low SNR in this case is a major one and the only way of its solving is synthesis of the dye with a high PL quantum yield. The PL relaxation time on the other hand is a main feature of the data reading rate and therefore selection of the appropriate recording material will allow to bring this parameter in accordance to parameters of modern optical discs. To achieve this goal the composite organic pyrazoline dyes where synthesized and investigated as effective medium with a PL quantum yield up to 60-70%, relaxation time less than 100 ns, PL wide spectrum and opportunity of two-photon absorption. These parameters were further improved by a method based on the performance of organic dye molecules in the zeolite matrix.

Line intensity ratio has been used in astronomy to calculate plasma density and temperature. This procedure is applied to monitor thin film growth in plasma-assisted deposition, it provides very useful information such as density and temperature of the plasma. The propose of this study is monitor variations of the plasma during deposition, using wide field optical spectroscopy and establish a relation with thin film stoichiometry. We report the preparation of inhomogeneous SiO_xN_y thin films, by sputtering.

A Cavity-Enhanced Direct Frequency Comb Spectroscopy (CE-DFCS) setup developed in our laboratory is described. We focus on the broadband spectrometer which is based on a Virtually Imaged Phased Array (VIPA). It can detect 3500 independent channels simultaneously, covering a bandwidth of 20 nm with a resolution of 800 MHz around a central frequency of 1.5 μm in a few microseconds. The bandwidth can be extended to 200 nm by rotating the grating of the VIPA spectrometer.

CO₂-laser DIAL ozone integrated measurements were performed in Madrid City. The results showed a dependence of ozone on UVB radiation, abundance of vehicle generated NO_X's and hydrocarbons. An average decrease of 12.0 ± 1.2 % of the intensity of vehicle traffic resulted in a lowering the ozone load by almost 14.0 ±1.4 %. Moreover, measurements of atmospheric ethylene, as a hydrocarbon representative and its relation with ozone, were performed. Ozone showed the same behaviour namely, a slow increase then reached a maximum at around 15:00 and back to 40-50 ppb level. The new data can stimulate the development of new local models to understand the dynamic underlying urban pollution.

Nowadays the production of counterfeit and low quality drugs affects human health and generates losses to pharmaceutical industries and tax revenue losses to government. Currently there are several methods for pharmaceutical product analysis; nevertheless, most of them depend on complex and time consuming steps such as sample preparation. In contrast to conventional methods, Laser-induced breakdown spectroscopy (LIBS) is evaluated as a potential analytical technique for the rapid screening and quality control of anti-diabetic solid formulations. In this paper authors propose a simple method to analyze qualitatively and quantitatively Active Pharmaceutical Ingredients (APIs) such as Metformin hydrochloride. The authors used ten nanosecond duration pulses (FWHM) from a Nd:YAG laser produces the induced breakdown for the analysis. Light is collected and focused into a Cerny-Turner spectrograph and dispersed into an ICCD camera for its detection. We used atomic emissions from Chlorine atoms present only in APIs as analyte signal. The analysis was improved using Bromine as internal standard. Linear calibration curves from synthetic samples were prepared achieving linearity higher than 99%. Our results were compared with HPLC results and validation was performed by statistical methods. The validation analysis suggests that both methods have no significant differences i.e., the proposed method can be implemented for monitoring the pharmaceutical production process in-situ in real time or for inspection and recognition of authenticity.

A new arrangement of 3 Langmuir probes to evaluate the electric potential and estimate the electron temperature in the LIBS plasma is introduced in this work. It consists of three nickel meshes (95% of transparency) on a basis for the sample in a vacuum chamber. The sample (a 50 cents coin) was analyzed at 9 different pressures (0.2, 0.4, 0.6, 0.8, 1, 2, 4, 6, 8 Torr). Measurements were made of the voltage signal induced in the electrodes relative to one another and to the sample. Information about the on-time and the duration of the plasma under the decreased pressure conditions can be extracted from these signals, which could in principle, be also correlated with the velocity of expansion of the plasma and the establishment of thermodynamical equilibrium in the system plasma-background gas. Additionally, we photographed the emitted light by LIBS plasma at maximum extension at different pressures by means of two digital cameras at the right angles to one another and to the laser beam. In each case, the expanded plasma contour was mathematically analyzed. In particular, the area of the plasma plume as recorded with the cameras was found to follow a simple relationship with the background pressure in a way not different from an ideal gas.

The spatial light modulators based on liquid crystal (LC-SLMs) have found applications in areas like beam shaping, optical tweezers, and microscopy. The use of these devices for pupil engineering has been an active research field. Many experiments with LC-SLMs involve the use of a digital camera, or even an additional LC modulator. Discrepancies in the refreshing rates of the modulator and the camera, or even between two nominally equal modulators, give rise to beating and intensity fluctuations, known as flicker, in the point spread function generated by the engineered pupil. In this paper we present a method for reducing the flicker caused by a liquid crystal on silicon (LCoS) SLM. It consists in reducing the temperature of the LCoS in a controlled form, in order to increase the viscosity of the liquid crystal, and with this reduce the amplitude of the intensity fluctuations due to the refreshing mechanism. We demonstrate that the flicker has been reduced to only the 25% of its initial value, when the LCoS is brought at 0 °C at a given gray level. Additionally, we found that the proposed reduction of temperature does not affect the dynamical range of phase control.

In this work, we reconstruct discrete image functions by means Bessel-Fourier polynomials. To measure the image reconstruction we use the Normalized image reconstruction error between the input and reconstructed images. We show that, a good reconstruction performance is found to be available for gray-level images. The reconstruction algorithm is implemented using the first forty zeros of the Bessel functions of the first kind. Experimental results are presented.

Nowadays people spent a lot of energy to reduce the temperature of walls buildings, by the use of air conditioner. There are a several solutions using green technologies to save energy, so we need to characterize this kind of greens technologies. Speckle interferometry is proposed to determine the variation of temperature on green buildings that relate the efficient use of energy spending in thermal comfort. There is a disadvantage to using thermal resistors sensors for the analysis of a wall area of sustainable technology, because these items can only measure a very small area, and it is very slow to make a average measurement of several points to have an estimate of the temperature. The analysis by speckle is favorable because it is very sensitive to any change made on a surface and this allows us to record the less obvious variation in the transmission of heat, as we can manipulate to measure considerable size areas. The use of speckle is more affordable and improve less economical resource than other methods.

In this work we present an optical system for the supervision of the operation of an induction motor. We used a Mach- Zehnder interferometer and cyclic interferometer for the measurement of the vibrations produced by the motor motion and obtain a frequency spectrum via a Fourier transform of the signal. According to the spectrum, we can know the operation conditions of the induction motor. The optical system consist of the Interferometer, a data acquisition board and virtual instrument.

In this work we have developed a design fringe projection method to obtain profilometry of a suitable object by using Dammann gratings encoded into an LCD as a modulator space and a monochromatic light source. Dammann grating are diffraction binary gratings commonly used to generate diffraction points with the same intensity in Fourier plane. Diffraction order and spatial frequency are parameter of grating design, several gratings types can be designed and projected on objects by controlling parameters of design.

The present work shows preliminary results of a phase unwrapping technique used in interferometry. Wrapped phase maps are the result of the modulus 2π ambiguities caused for the phase recovery function arctan. Here we present a recursive n-order phase unwrapping system that removes the ambiguities, it's robust to noise and fast. The system is able to recover the unwrapping phase in presence of high noise, according to stability of the system that can be controlled. This high noise causes line sequential integrations of phase differences to fail. The system is not numerically-heavy in comparison with other methods that tolerate the noise. The application areas of the system can be: optical metrology, magnetic resonance, and those imaging systems where information is obtained as a demodulated wrapped phase map.

The cavitation phenomenon has been extensively studied by numerous researchers because the collapse of the cavitation bubbles is responsible for a number of phenomena of interest in the fields of science and engineering, such as: Luminescence, sonochemistry, cavitation damage, ultrasonic cleaning, etc. The most common methods to produce cavitation bubbles are: pulsed lasers, electroforming, sonophoresis, radiofrequency, and Venturi effect. In this paper we are interested in a method called thermocavitation, which is induced by low power, CW laser radiation in a highly-absorbing solution of copper nitrate (CuNO₄) dissolved in water. The bubble formation occurs when an overheated region (~300°C) is created followed by explosive phase transition and the formation of vapor-gas bubbles, which expand and later collapse very rapidly emitting intense acoustic shockwaves. The characteristic effects of bubble dynamics, in particular the formation, growth, collapse and a high-speed liquid jet at the moment of collapse are recorded using a high speed video camera (Phantom V7, Version 9.1) with frame rates of up to one hundred thousand frames/s at different laser powers (62 to 200 mW). The shockwaves are sufficiently energetic that they may be employed to generate deep lesions in biological tissue models, such as agar gel and chicken breast samples as a preamble to future studies on thermocavitation for tissue ablations. This approach of achieving thermocavitation is attractive due to the fact that it is generated with low power CW lasers which decrease cost and complexity relative to other approaches.

We study the diffraction of Gaussian pulses and beams within the framework of boundary diffraction wave theory. For the first time the boundary diffraction wave theory is applied to pulsed Gaussian beams, and it is shown that the diffracted field of a pulsed Gaussian beam on a circularly symmetric aperture can be evaluated by a single 1D integration along the diffractive aperture of every point of interest. We compare the theoretical simulations to experimental measurements of ultrashort pulses diffracted off a circular aperture, an opaque disc, an annular aperture, and a system of four concentric annular apertures. Using the recently developed SEA TADPOLE measurement technique, we obtain micron spatial and femtosecond temporal resolutions in the spatio-temporal measurements of the diffracted fields.

We have investigated a nonlinear pulse reshaping towards parabolic pulses in the passive normal dispersive optical fibers. We have found that pulses with parabolic intensity profile, parabolic spectrum and linear chirp can be obtained due to the passive nonlinear reshaping at the propagation distance exceeding a few dispersion lengths. These pulses preserve parabolic profile during subsequent pulse propagation in a fiber. We have examined the influence of initial pulse parameters and fiber parameters on the resulted pulse shape.

We analyze the Gaussian temporal envelope of pulses with a duration of 20fs and a carrier wavelength of 810nm at the paraxial focal plane of an achromatic doublet lens. The incident pulse beam is well-collimated and we use the Seidel aberration theory for thin lenses. In a set of cemented thin lenses with the stop at the lens, there is only spherical aberration, coma, astigmatism and field curvature. The distortion aberration introduced by the lens is zero. We analyze the effect of these aberrations in the focusing of ultrashort pulses for homogenous illumination.

We analyze the Gaussian temporal envelope of pulses with an initial duration of 200fs and a carrier wavelength of 810nm at the paraxial focal plane of an achromatic doublet lens designed in the IR region. The Seidel aberrations for thin lenses are evaluated for a well-collimated beam. We analyze the effect of these aberrations in the focusing of ultrashort pulses for gaussian illumination and experimental results are presented for 200fs incident pulses and for three incident angles: 0°, 5°, and 8°.

The interplay between chromatic dispersion and nonlinear effects is patent. Once a photonic crystal fiber (PCF) preform has been prepared, changing the parameters that control the fabrication process it is possible to adjust the dispersion properties of the fiber. In addition, it is very useful to develop postprocessing techniques that enable a fine adjustment of the dispersion along a section of PCF. The tapering of PCF, using a fusion and pulling technique, has been established as a rather useful technique to engineer the dispersion properties along tens of centimeters. Some of our recent experiments demonstrate that the use of erbium doped PCF enables an optical control of the dispersion through optical pumping of the rare earth ions. Our interest is focused on the exploitation of nonlinear PCF for the development of fiber light sources. Thus, we will present several experiments on supercontinuum and photon pairs generation, through degenerated four-wave mixing (FWM), in order to illustrate the control that one can achieve on the optical spectra of these light sources as a function of different dispersion control approaches.

We theoretically demonstrate by using fractional calculus tools the linking between the instantaneous phase profile of a given temporal optical pulse and its photonics semi-differintegration, i.e. a 0.5th-order differentiation/integration. In both cases, the signal's temporal phase can be retrieved by simple dividing two temporal intensity profiles, namely the intensities of the input and output pulses of a spectrally-shifted 0.5th-order differentiator/integrator. In both cases, we obtained simple analytical expressions for the instantaneous frequency profile. We numerically prove the viability of these proposals.

The mirrorless backward optical parametric oscillator (BOPO), where the signal and idler waves are propagating in opposite directions, will establish a distributed feedback mechanism and thus optical parametric oscillation without the need to apply mirrors or external feedback to the cavity. It has been recently demonstrated experimentally by exploiting the periodic poling technique in second-order nonlinear crystals, that the sub-micrometer structured medium achieves an efficient quasi-phase-matching of the three wave interaction in the backward configuration. A remarkable property of such BOPO is the high degree of coherence of the backward wave component, whose spectrum may be several order of magnitudes narrower than that of the pump, due to the convectioninduced phase-locking mechanism. Experimentally and numerically proved the transfer of coherent phase modulations from the pump wave to the parametrically down-converted waves, we show here that this is also possible for a broad bandwidth spectrally incoherent pump. In order to accurately describe the nonlinear counter-propagation dynamics of the three dispersive waves, we have developed for the first time to our knowledge a new numerical scheme which combines the method of the trajectories usually employed to solve the three-wave interaction and the intraband group velocity dispersion effect is performed in the spectral domain with the help of the Fast Fourier Transform (FFT) technique. The model accurately conserves the number of photons and the Manley-Rowe invariants. This allowed us to predict various configurations of MOPOs in which, thanks to the convection-induced phase-locking mechanism, a highly coherent backward wave is spontaneously generated from a highly incoherent pump wave.

We consider the optical nonlinearity enhancement, which is obtained for rubidium vapor by using beams with mutually orthogonal polarizations. The simple three-level model and numerical estimations for a full transition model are reported. Different from the traditional Kerr nonlinearity, the vectorial mechanism nonlinearity strength diminishes for higher intensities, as well as for low ones, and optimal intensity level exists.

In this work we study experimentally and numerically a passively mode-locked figure-eight fiber laser that includes a polarization-imbalanced Nonlinear Optical Loop Mirror (NOLM), whose switching power can be adjusted through a wave retarder plate. The laser emits broadband noise-like pulses with a bandwidth that can exceed 50 nm. The pulses are actually sub-nanosecond wave packets with an inner fine structure of sub-ps pulses with random amplitude and duration. The duration of the pulses as well as their spectral width can be adjusted through the variation of the NOLM switching power. Numerical simulations are in good agreement with experimental results, confirming in particular the strong dependence of the pulse properties on the value of the NOLM switching power, although NOLM switching alone does not explain the appearance of the noise-like pulsing mode. The properties of this kind of pulses, like their wide bandwidth and energy, make them attractive for applications like supercontinuum generation and metrology.

In this work, we analyse the use of a micro-machined deformable membrane mirror (MMDM) to shape femtosecond pulses. We present the Spectral-Phase-Influence-Matrix constructed by an inversion method. Spectral-Phase-Influence- Matrix represents a novel and direct method to estimates the Spectral Phase design from a given actuator voltage settings in a single step. Numerical and experimental results are presented.

We report on the interaction of high repetition rate (MHz) Ti: sapphire laser pulses with a spiropyran polymer (MIC1). Such a polymer is photochromic, wich has potential applications in integrated optical devices. A thin film of polymer deposited on a glass substrate is irradiated with ultrashort pulses (66 fs) from a Ti: sapphire laser. We demonstrate that it is possible to induce an absorption band in the visible by the use of femtosecond pulses via a two-photon excitation process; this might be useful to accomplish waveguide-like structures formation with photochromic response.

In this works, synthesis and evaluation of the luminescence properties of novel polythiophenes derivatives derived of 3- alkylthiophenes (alkyl=hexyl, octyl) and thiophenes functionalized with a NLO chromophore: 2-[Ethyl[4-[2-(4- nitrophenyl)ethenyl]phenyl]amino]ethanol are reported. The optical response of copolymers films obtained by spin coating technique when they were excited optically was analyzed. The fluorescence signals measured to about 650 nm when the copolymers were excited at 488 nm (blue light) were studied to different excitation powers. The optical response of the copolymers films shows a change ratio of around 6%/mW. The evaluations of photoluminescence properties of conjugated polythiophenes are important due to their potential applications in light-emitting diodes (LEDs), solar cells and chemical sensors.

The transmission of an intense light beam through a thin nonlinear sample has been extensively studied, like in self phase modulation experiment and Z-scan technique, with different approaches: the Gaussian decomposition method, the Huygens-Fresnel principle, the diffraction theory, etc., The nonlocality in the response of the media in general leads to solve more than one differential equation. In this work we present a simple model to calculate, in a numerical way, the on axis far field intensity in a Z-scan experiment or the far field pattern in spatial self phase modulation experiment by means of the diffraction theory and taking into account the locality of the thin nonlinear media. The obtained results show that the peak-valley separation distance and the transmittance difference in a Z-scan experiment and the number of rings, size and intensity distribution of the far field pattern in the spatial self phase modulation experiment are functions of the locality in the nonlinear response of the media. The proposed model describes in good approximation experimental results for samples, like absorbing liquids, liquid crystals, metal nanoparticles, etc., with different kind of nonlinear response. This model is valid for any value of the nonlinear phase shift.

Plasmonics is the most promising field appointed to continue the predictions of the Law of Moore as well as for the confinement of light on a subwavelength spatial scale, allowing the breaking of the diffraction limit. In that direction, we have produced by ion implantation, interesting nanocomposites with very attractive optical properties. Recently, a double implantation of Si and Ag ions in silica, with subsequent thermal treatments in appropriated atmospheres, allowed us to obtain two layers: one of Si nanocristals (NCs), and other of Ag nanoparticles (NPs). This arrangement shows an enhancement of the emission of Si nanocrystals (NCs) in a new, totally integrated configuration. The synthesis of the system by ion implantation offers a total protection of the optical active agents from environmental effects such as oxidation, additionally assuring a high degree of homogeneity. We present a photoluminescence excitation study (420-500 nm) of Si NCs, with and without the presence of Ag nanoparticles (NPs), both embedded in a matrix of SiO₂. The level of saturation for Si NCs is independent of the excitation wavelength, but for Si NCs in the presence of Ag NPs, a saturation level arises for excitation wavelengths near the absorption band of the surface plasmon resonance of the Ag NP (325-475 nm). The increase of both, the values of saturation and excitation cross-section of Si NCs in the presence of Ag NPs, is an evidence of the optical interaction between the metal NPs and Si NCs studied in this work. This suggests a decrease of the lifetime of Si NCs photoemission due to the interaction with the Ag NPs.

Films made of Polymethylmetacrylate (PMMA) and doped with dipolar second order nonlinear optical chromophores were studied by UV-visible spectroscopy and transmitted resonant Second Harmonic Generation technique. The chromophores were non-centrosymmetrically oriented by a Corona poling field. The UV-visible spectra were measured in poled films at normal incidence as function of their poling temperatures (60, 80 and 100°C) and they were analyzed in terms of the Second Order Parameter (A₂). The Second Harmonic Generation (SHG) signals in the films were measured in-situ as function of the poling time at several incidence angles for each poling temperature. The stability of the SHG signal was also determined, by turning off the Corona field but leaving the films at their original poling temperature. The films were of two different kinds: amorphous and nanostructured. All the films doped simultaneously with chromophores and surfactants showed long-range ordered nanostructures. Two kinds of surfactants were used during the synthesis of the films: ionic and neutral, both of them induced long-range order in the structure of the PMMA, but only some of the nanostructured films exhibited enough large SHG signals. The second order nonlinear optical response of the nanostructured films was compared with the corresponding response of the amorphous films. The long-range order in the films was detected by X-Ray Diffraction (XRD).

The observation of ultrafast fundamental processe in real time is a key to exploring the dynamic behaviour of matter. In order to be able to do these observations, pulses shorter than the processes under scrutiny have to be generated. Over the past decade novel ultrafast optical technologies have pushed the duration of laser pulses close to its natural limit, to the wave cycle, which lasts somewhat longer than one femtosecond (1 fs = 10EXP-15 s) in the visible spectral range. About ten years ago these pulses were used to generate single isolated attosecond pulses in the extreme ultraviolet (XUV): Atoms exposed to a few oscillation cycles of intense visible or near-infrared light are able to emit a single electron and XUV photon wavepacket of sub-femtosecond duration. Precise control of these sub-femtosecond wavepackets have been achieved by full control of the electromagnetic field in few-cycle light pulses. These XUV pulses together with the few-cycle (few-femtosecond) laser pulses used for their generation have opened the way to the development of a technique for attosecond sampling of electrons ejected from atoms or molecules and solids.

We present the numerical modeling of the interaction between a spatial soliton and a surface plasmon polariton under leak and strong coupling in the following two cases: at metal/dielectric/Kerr structures and metal/Kerr structures in 1D. Here, we solved the vectorial and nonlinear wave equation using a novel iterative method based in self-autoconsistency, and we found two kinds of nonlinear stationary solutions called odd and even modes. On the other hand, the propagation of the stationary solutions is performed for the metal/Kerr system, and quantitatively it shows that odd modes are more stable than even modes when the spatial soliton and surface plasmon are strongly coupled. Also, we analyzed the influence of the dielectric layer between the metal and Kerr media, and we discuss their implication and feasibility for applications in photonic nanodevices. Additionally, the advantages and disadvantages of the numeric method used to obtain the stationary solutions are discussed. The results obtained in this work are reproducible and contributes with new information for the development of power-tunable photonic nanocircuits based in nonlinear plasmonic waveguides.

We analyze the Gaussian temporal envelope of pulses with an initial duration of 10fs and a carrier wavelength of 810nm along the optical axis of an achromatic doublet designed in the IR region with numerical aperture 0.15 and focal length of 40mm. The diffraction integral is solved by expanding the wave number around the carrier frequency of the pulse in a Taylor series up to third order, and then the integral over the frequencies is solved by using the Gauss-Legendre quadrature method. The numerical errors in this method are negligible by taking 96 nodes and the computational time is reduced by 95% compared to the integration method by rectangles. We will show that the third-order GVD is not negligible for 10fs pulses @810nm propagating through the low numerical aperture doublet and its effect is more important than the propagation time difference, PTD. This last effect, however, is also significant.

We present an experimental 8-port Balanced Homodyne Detector at 1550 nm wavelength, operating in free space, implemented with polarization devices to produce a circularly polarized local oscillator, splitting its In-Phase and Quadrature components to beat separately with the weak coherent incoming signal. This allows the simultaneous measurements of the 2 quadratures at the price of an additional noise due to the vacuum fields that leak via the unused ports, resulting in a modified Husimi function for joint probability distribution for the quadrature components. These schemes require the proper optical phase synchronization between the local oscillator and the incoming field, which constitutes a challenge for weak coherent state reception. To achieve this we designed and implemented an optical Costas loop; the feedback loop (especially the loop filter) which is a result of the optimal design has an impact on the mutual information between transmitter and receiver, being this parameter a condition to generate the cryptographic key. We present experimental and theoretical results on the performance of the mutual information between the transmitter and the receiver due the phase error for different photon numbers.

The optical characterization of nonlinear media through the Z-scan technique considers initially a thin medium (with a thickness much less than the beam depth of focus). It has been observed that increasing the thickness of the medium the transmittance increases, this means that n2 increases, for this reason we will present a numerical model to determinate the minimum thin and the maximum thick medium limit. A thin medium is considered as a thin lens with focal length F¹ and a thick medium can be regarded as a set of such thin lenses set with focal lengths F², these lenses are contained in a medium whit a refraction index different than air. This analysis is made through Matlab using the theory of Gaussian beams, ABCD matrices and the q parameter, elementary theory in the development of this work, where the main feature of this model is that the nonlinearity type of the medium is considered as an integer constant in its focal length³. We present the graphs obtained from Z-scan for thick medium with both thermal and Kerr nonlinearities.

We study, theoretically and experimentally, a new type of a multi-phonon Bragg light scattering in an optically anisotropic medium. A four-phonon Bragg anomalous light scattering in a tellurium dioxide crystal was observed using a light-blue optical beam of about 1 W in power from an argon gas-laser. Just the Bragg regime of light scattering was assured experimentally and a pentet of the light orders was distinguished and investigated.

The study of bubbles and bubbly flows is important in various fields such as physics, chemistry, medicine, geophysics, and even the food industry. A wide variety of mechanical and acoustic techniques have been reported for bubble generation. Although a single bubble may be generated with these techniques, controlling the size and the mean lifetime of the bubble remains a difficult task. Most of the optical methods for generation of microbubbles involve high-power pulsed laser sources focused in absorbing media such as liquids or particle solutions. With these techniques, single micron-sized bubbles can be generated with typical mean lifetimes ranging from nano to microseconds. The main problem with these bubbles is their abrupt implosion: this produces a shock wave that can potentially produce damages on the surroundings. These effects have to be carefully controlled in biological applications and in laser surgery, but thus far, not many options are available to effectively control micron-size bubble growth. In this paper, we present a new technique to generate microbubbles in non-absorbing liquids. In contrast to previous reports, the proposed technique uses low-power and a CW radiation from a laser diode. The laser light is guided through an optical fiber whose output end has been coated with nanostructures. Upon immersing the tip of the fiber in ethanol or water, micron-size bubbles can be readily generated. With this technique, bubble growth can be controlled through adjustments on the laser power. We have obtained micron-sized bubbles with mean lifetimes in the range of seconds. Furthermore, the generated bubbles do not implode, as verified with a high-speed camera and flow visualization techniques.

We analyze theoretically the (spectral) spatial coherence and polarization properties in fluctuating surface plasmon fields generated at a lossy, thin metal film surrounded on both sides by air. Using rigorous electromagnetic interactions at the interfaces and the theory of optical coherence in 3D fields, we show that new coherence and polarization effects may occur in such plasmon fields. In particular, coherence lengths extending over several thousands of wavelengths, or coherence lengths significantly shorter than the wavelength of light in vacuum, can be found at certain frequencies. Using a recent 3D formulation, we also examine the degree of polarization in such random surface plasmon fields. We show that the field may be partially polarized in the immediate vicinity of the excitation of the surface plasmon modes, even though it is fully polarized farther away. In addition, we demonstrate that an increasing number of modes leads to a more polarized field above the plasmon excitation region, with the degree of polarization effectively independent of the height.

We describe and theoretically analyze the self-imaging Talbot effect of entangled photon pairs in the time domain. Rich phenomena are observed in coherence propagation along dispersive media of mode-locked two-photon states with frequency entanglement exhibiting a comblike correlation function. The observed effect suggests a straightforward and implementable way to transfer remotely frequency standards embedded on ultracompact quantum light sources.

The radiation pressure forces for Au nanoparticles in the Rayleigh regime under the influence of a coherent source of infrared light from 0.7-1.5 μm of a Gaussian beam with fundamental mode corresponding to the TEM₀₀ mode are studied. An intensity distribution of the source in terms of the spot size and power are considered to analyze the gradient, scattering and absorption forces on a sphere located arbitrarily on a Gaussian beam. The results have shown, through an analysis stability, the optical manipulation is better suited for longer wavelengths, small particles, and a beam waist significantly reduced.

The multiple functions and potential applications of nanotechnology have become a necessary and powerful tool in scientific work everyday. Nanotechnology is interdisciplinary science involving physics, chemistry, biology, materials science and wide range of engineering disciplines. His versatility has led to an increasing use in wide range of fields. For example, electronic engineering has shown an interest growing in the design of nanodevices due to continued miniaturization of them. The investigations have focused on the manufacture of electronic circuits and their applications complex systems, in addition to this, nanotechnology already plays an important role in development of new materials with tailored features and chemical properties, so their study is important today. Nanosensors have been under investigation for some institutions in recent years. A nanosensor is a device built on an atomic scale based on measurements nanometers, whose purpose is mainly to obtain data on the atomic scale transfer so they can be easily analyzed. In this work We study wave propagation in a low-dimensional planar nano-waveguide, to establish the principle of operation of an optical structure to propose the design of a nanosensor.

Gold nanoparticles (AuNPs) have proven to be powerful tools in various ultrafast photonic, plasmonic and nanomedical applications. Numerous advances in the use of AuNPs include research on their interesting and remarkably fast changes influenced by Surface Plasmon Resonance excitations. Within this work we report theoretical and experimental results for the physical mechanisms that originate a nonlinearity of refractive index during different temporal regimes for a high-purity silica matrix containing Au nanoparticles. The nanocomposites were prepared by ion implantation into a silica matrix, followed by a thermal annealing. We used an optical Kerr gate with 80 fs pulses at 830 nm and a vectorial self-diffraction technique with 26 ps and with 7 ns at 532 nm in order to investigate the magnitude and response time of the resulting third order nonlinearity. In all cases we were able to measure and identify an electronic polarization responsible for the nonlinear refraction. For the pico- and nano-second near resonance irradiations, a contribution of a thermal effect could be stimulated and then the optical Kerr response enhanced. The presence of saturable absorption for the pico- and nano-second experiments was measured. We observe that our samples behave like waveguides in the near infrared spectrum and we estimate that they posses potential applications for all-optical switching devices.

We present a simplified model for describing the propagation of optical solitons through optical lattices. A pair of second order differential equations for the transverse coordinates of the intensity centroid of the soliton are deduced from the nonlinear Schr¨odinger equation. As an advantage over the quasiparticle approach we avoid the need of integrating algebraically the soliton intensity profile over the lattice. This allows modeling soliton motion even for non-symmetric lattice potentials, as that presented by an outer ring of a modulated Bessel lattice . We discuss in detail the range of applicability of our model and use it to predict the soliton motion in optical lattices generated by plane-waves, Bessel beams, and others.

We present a nonlinear optical study using standard Z-scan technique at the picosecond regime, in a nanostructured material containing both quasi-spherical silver nanoparticles and silicon quantum dots, and comparing its response to those from similar systems, one with only silicon quantum dots, and another with only silver nanoparticles. The study was done using different wavelengths, 355 nm and 532 nm, which are localized at both sides of the surface plasmon resonance of the Ag nanoparticles, and 1064 nm, which is localized well far away of it. In general, we have observed that the larger optical nonlinear response came from the sample with silver NPs. However, the combined system showed a positive nonlinear refraction below the plasmon resonance (355 nm), changing to a negative value for wavelengths above resonance (532 nm and 1064 nm). We observed also, for the combined system and for the three wavelengths used, a saturation of the nonlinear refraction index as a function of the incident irradiance.

In this paper we report the linear and non-linear optical properties of metallic nano-clusters in α-Al₂O₃ fabricated by ion implantation (from 2 to 8×10¹⁶ ions/cm²). Thereafter, the samples were annealed at temperatures from 600 to 1100 °C in oxidising, reducing atmospheres. Once spherical nano-particles were synthesized, the samples were further irradiated with Si⁺⁺⁺ with different energies and fluences to control the achieved anisotropy. As a result of the ion implantation mostly F⁺ color centers were formed. After thermal annealing they capture an electron to form F centers or combine to form a F₂⁺ center. Also, the photoluminescence signal from Al⁺ interstitials appears. Regarding the non-linear optical response, the spherical-like Au nano-crystals embedded in sapphire show a positive non-linear absorption at 355 nm and negative non-linear absorption at 532 nm, which shows saturation when increasing the incident irradiance. They also present positive non-linear refraction at 532 nm, which is null at 355 nm. For the anisotropic systems, a larger birefringence than natural values was measured in the visible range by ellipsometry means.

Fast optical self-focusing has been observed in a homeotropic nematic liquid crystal cell. This nonlinearity is induced by an intensity modulated infrared laser having a peak power of 160mW, a pulse repetition rate of 150Hz, and a duty cycle of 0.05 and launched with extraordinary polarization. During these experiments the illumination time is kept at 0.3msec and the ambient temperature is controlled. We have observed that self-focusing propagation depends on ambient temperature, laser power and duty cycle. Notably, when illuminating with a continuous beam having the same corresponding average power, only diffraction can be observed. These results suggest that the nonlinearity is produced by a combination of thermal effects and molecular reorientation that leads to changes in the order parameter. Further optical experiments and thermal calculations have been conducted to identify the responsible mechanism for the self-focusing of the laser beam. It has been found that soliton formation can be achieved if the parameters as ambient temperature, pulse repetition rate and duty cycle of the laser are set to optimal conditions. Although, this nonlinearity in a liquid crystal cell has been already demonstrated for transverse illumination, the presence of beam propagation with self-focusing has not been reported yet. The fast nonlinearity reported in this work has the potential to generate a number of new applications of liquid crystals.

Resonant cavities based on whispering gallery modes (WGM) have high quality factor, Q. This property is highly desirable for the design of a variety of devices. The quality factor is larger for larger systems, but, at the same time the density of modes increases, and not as regularly spaced frequencies, because modes of different kind superpose. For a dielectric cylinder, the modes are characterized by their azimuthal and radial behavior. The complex frequencies corresponding to the modes have a strong dependence on the radial order. We use the finite difference time domain method, to study the transmission of light by two prisms with a dielectric cylinder between them. The system acts as a filter with sharp peaks of modes of high Q. The coupling to the modes can be controlled by changing the distance of separation between the prisms. For large coupling, the full width at half maximum of the transmission peaks increases, being more noticeable for the high Q modes.

In the present work, oxalic amorphous porous anodic alumina membranes (AAM) with highly ordered porous arrays and average nanometric porous dimensions of 70 nm in diameter and 37 microns in depth (nanotubes) were prepared and successfully used as hosting matrix for C₆₀ and C₇₀ fullerene compounds. Atomic force microscopy (AFM) studies were performed on the hybrid samples in order to explore surface morphology and optimal insertion of these molecular systems into the AAM environment. The cubic nonlinear optical (NLO) properties, such as nonlinear refraction and absorption of the hybrid samples were studied via the Z-Scan technique in order to evaluate their NLO-performance. Hybrid AAM with fullerene compounds have shown outstanding NLO-activity with positive NLO-refractive coefficients.

The Entanglement of quantum systems is a key aspect in order to understand the dynamics and behavior of mixed systems (density matrix) as bipartite systems of quantum bits (q-bits). A quantifiable measure widely used is the "entanglement of formation" of a mixed state, defined as the minimum number of singlets needed to create an ensemble of pure states that represents the density matrix of the system. Considering a double quantum dot system coupled cavity type Jaynes-Cummings investigate the entanglement between two quantum dots, immersed each in its own cavity, showing analytically that entanglement has a very interesting effects such as temporal evolution including the so-called sudden death effect.

The following work presents the linear and nonlinear optical (NLO) properties for two ligands (L1-L2) derived from cinnamaldehyde and their corresponding boron complexes (B1-B2). These organic molecules have a backbone with electronic π-systems possessing different "push-pull" features. The structure confirmation of compounds L1 and B1 was made through X-ray diffraction analysis, wherein is observed that planar conformation is conserved after boron complexation on B1. Linear absorption of ligands and boron complexes shows a red shift after boron complexation which could be attributed to more efficient intramolecular charge transfer. Second and third-order NLO responses were performed by Electric Field Induced Second Harmonic (EFISH) Generation technique at 1.9 μm and Third-Harmonic Generation (THG) at 1.9 and 1.067 μm, respectively. Experimental results showed an increment on the hyperpolarizabilities values from ligands to boron complexes which are attributed to N→B coordinative bond. The first hyperpolarizability increased by factors of 3 and 2 from L1 to B1 and L2 to B2, respectively. Individually, these studies demonstrate that B1 is the strongest NLO compound, showed values of first hyperpolarizability 126×10^-24 and second hyperpolarizability 35×10^-24.

In the aim to understand the nature of the propagation of an electromagnetic field in the near region, we study the interactions between an evanescent field and two different samples of spherical dielectric nanoparticles, i.e. a set of five particles and a single one. Each sample was studied in separated experiments. This is made by using a Photon Scanning Tunneling Microscope (PSTM) in the constant distance mode. We also analyze the obtained images and determine that the optical images show mainly interference between the evanescent field and the reflected field on the surface of the nanoparticles. Finally, we found that the perturbation of the evanescent field, produced by imperfections on the substrate, is negligible in comparison with the interactions intensity.

Emerald, natural and synthetic, are the subject of study by means of optical spectroscopy techniques. Particularly, natural emeralds have been considered as a gemstone in jewelry not being so the synthetic ones. But, in general, the properties of these are very good for applications, for instance as a laser system, due to the impurities control. In this work a comparison between natural and synthetic emeralds is done. Chromium ions are the main responsible of the characteristic fascinating green color of these gemstones, entering in the crystals in octahedral sites. Absorption at room temperature show up two broad bands in the visible region and two narrow bands called the R-lines. That spectrum corresponds to trivalent chromium ions in an octahedral site, as it happens in ruby and alexandrite. On other hand, photoemission arises in the range 640-850 nm. at room temperature . It is shown that the luminescence spectra changes as the temperature is lowered. The effect on the main peak of luminescence when high pressure is applied on small samples of emerald shows as a linear function.

Phthalocyanines (Pc) based compounds having central metallic atoms of Ni were successfully embedded in mesoporous silica gels via a catalyst-free sol-gel (sonogel) process in order to fabricate optically active solid-state hybrid glasses in both bulk and thin film formats at different dopant concentrations. The organic-inorganic hybrid composites obtained at room temperature processing showed stable mechanical performance, controllable geometrical shapes, good transparency and homogeneity suitable for linear and nonlinear optical (NLO) characterizations. Hybrid samples were studied via the NLO third-harmonic generation (THG) technique. AFM studies, epi-microscopy surface evaluation, refractive-index measurements and UV-Vis spectroscopy studies were also performed in selected bulk and film samples. The morphological and spectroscopic results showed a homogeneous dispersion of the organometallic compounds within the highly pure SiO₂-sonogel network. Moreover, Brewster's angle measurements have demonstrated the feasibility of tuning the refractive index of the samples by varying the chromophore dopant concentration. Additionally, the electronic absorption spectra showed band shifts in the two characteristic bands of the organometallic compound within sonogel environment, which evidence the formation of molecular H-aggregates for the developed hybrids and the consequent modifications of their optical properties. Finally, THG measurements in hybrid film samples exhibited an important NLO activity. We conclude that the optical effects of these composites can be tuned as function of the nickel-Pc concentration and that the sonogel matrix mainly acts as an inert protective shell, giving stable mechanical and thermal properties to the guest dopant compounds.

We generalize Mie scattering theory to describe the scattering of light with orbital angular momentum (OAM). We apply our results to the analysis of scattering by gold nanoparticles and compare the angular distribution of the scattered light for plane waves and light with OAM. The multipole expansion for scattered OAM waves depends on the localized surface plasmon modes that can couple to incident light carrying a well-defined amount of azimuthal charge (or l-number) at a particular wavelength. We study here the properties of Mie scattering of OAM waves by nanoparticles located at the beam waist as a function of the size of the particle and of the frequency and content of azimuthal charge of the incident wave.

Soliton behaviour in higher order electromagnetic (EM) modes in commercial highly nonlinear photonic crystal fibre (PCF) was investigated by mapping spatial and spectral emission. A femtosecond mode-locked Titanium:Sapphire laser was used to generate supercontinua within a set of higher-order electromagnetic modes by piezoelectric control of the spatial field input to the PCF. Coupling pump wavelengths within the normal dispersion regime for the fundamental EM mode into higher EM modes resulted in the emission of blue light, characteristic of higher order soliton fission, in higher order EM modes. Detailed spectral measurements across the spatial mode field output from the PCF, showed different spectral components of the generated continua occupying different spatial electromagnetic modes. In particular, the blue emission was found to be structured with spectral wavelengths at 440 nm and 450 nm associated with different spatial EM modes. These new measurements are the first to detail high order solitonic interactions in higher order electromagnetic modes and to record different spectral emission wavelengths associated with different higher order spatial modes. These results are not well matched to current theoretical models for supercontinuum generation developed for the fundamental EM mode. The lower zero dispersion wavelengths associated with higher EM modes in PCF enable previously undetected engagement of these modes in supercontinuum generation and propagation.

This paper we analyzed three alternatives for optical amplification used to extend the reach of optical fiber link for the transport of RoF (Radio over Fiber) in view of 54 MHz RF signals for wireless applications.

An algorithm for the analysis of the double clad fiber design is presented. The algorithm developed in the MATLAB computing language, is based on ray tracing method applied to three-dimensional graphics figures which are composed of a set of plans. The algorithm can evaluate thousands of ray paths in sequence and its corresponding pump absorption in each of the elements of the fiber according to the Lambert-Beer law. The beam path is evaluated in 3 dimensions considering the losses by reflexion and refraction in the faces and within the fiber. Due to its flexibility, the algorithm can be used to study the ray propagation in single mode or multimode fibers, bending effects in fibers, variable geometries of the inner clad and the core, and could also be used to study tappers.

In this paper, we present the results of theoretical and experimental study of the actively Q-switched erbium-doped fiber laser realized in symmetric configuration. We extend the traveling wave model to this type of fiber lasers and show that such laser permits one to obtain easily the short giant pulses (17 ns on 3 dB level) with small adjacent subpulses. Our model accounts all point losses including loss on the fiber splices and other intra-cavity devices and also the distributed losses such as the active fiber background loss and loss owing to excited state absorption observed in erbium-doped fibers. We compare the experimental data with the modeling results and reveal their good matching, once the laser parameters are properly accounted in the model.

In this paper, a new method for measuring the nonlinear refractive index by using the nonlinear dynamics generated in optical fiber ring resonator (OFRR) is proposed. In OFRRs, input light and circulated light components are added in succession, and then, result in forming an interference output. The OFRR output exhibits nonlinear dynamics such as a chaotic state due to the optical Kerr effect, as the input light power increases. In the bifurcation diagram, the output power indicates peaks in the input power range lower than the bifurcation point at which the output changes from stable to periodic state. It is found that the input power at the peak shifts, dependent on the nonlinear refractive index. The nonlinear refractive index can be estimated by applying the measured input power giving the peak point to the numerical relationship between the input power and the nonlinear refractive index. In experiments the nonlinear refractive index of the two pure silica core fibers with different cutoff wavelength was estimated as n₂=0.97×10^-22[m²/V²] and n₂=1.06×10^-22[m²/V²] which are in good agreement with those reported previously.

The development of efficient in-fiber amplitude modulators that operate in the MHz frequency range has enabled some recent advances in actively mode-locked all-fiber lasers. Our approach is based on the excitation of a standing acoustic wave along the fiber, which modulates the coupling between modes at twice the frequency of the acoustic wave. Among the remarkable features of these in-fiber modulators, we mention the high peak power damage, high modulation depth, broad bandwidth, easy tunability in optical wavelength and low insertion losses. The in-fiber modulation is crucial for the implementation of all-fiber compact and robust lasers. The experimental characterization of different cavity configurations as a function of the radio frequency voltage that controls the modulator, the length of the active fiber, the overall dispersion of the cavity, etc., has led to an improved operation of the lasers: output optical pulses of 34 ps temporal width, 1.4 W peak power and 4.7 MHz repetition rate, at the emission wavelength of erbium.

On this work we present a Titanium:Sapphire laser with simultaneous dual wavelength operation in the 890 nm region. Dual wavelength operation is obtained using a novel four stage birefringent filter in which we can control wavelength separation by tilting one of the filter elements. The laser operates in continuous wave pumped by a 5.5 Watts 532 nm source producing 100 mW at both wavelengths. We obtained wavelength operation with separation of 2.0 nm to 3.0, corresponding to frequency separation between 0.8 THz to 1.2 THz. The ultimate goal is the development of a source in the terahertz (THz) region of the electromagnetic spectrum for medical applications.

Photonic crystal optical fibers have much more degrees of freedom concerning the geometries and index contrasts than step-index fibers; therefore, the theoretical analysis of their performance is usually based on the finite element method. In this work, taking advantage of the similarities observed for twisted single-mode fibers: standard (SMF-28 and SMF- 28e) and hexagonal photonic fibers, we propose that in regard with polarization performance, photonic fibers can be described using a simpler model based on classical polarization optics. The main advantages of the matrix model we propose lie in its accuracy and generality: for each one of the selected wavelengths and input states of polarization, it allows a precise prediction of the output polarization state. The comparison of the experimental results measured for standard and photonic fibers with the theoretical model predictions indicates that in both cases, twist induced birefringence is produced not only by the medium's photoelasticity, but also by the waveguide (cladding/core structure and asymmetry) modification. In addition, for the photonic fiber, the non-symmetrical response to right and left twist allowed the identification of an initial twist as part of the residual elliptical birefringence.