This PDF file contains the front matter associated with SPIE Proceedings Volume 8697, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

The goal of the ELI (Extreme Light Infrastructure) project is to build a laser centre with the worlds highest power output pulsed laser in the locality of Dolní Břežany near Prague. Presented paper offers first glance to the insight into continuous and pulsed beam interaction with various optical systems which causes beam's spatial and temporal transformation. Complexity of this problem is illustrated in need of geometrical and physical optics knowledge, numerical simulations, material engineering and many others. This paper is focused on the field trace simulations in various software environments for both simple and more complex optical systems.

We present a method for including an arbitrary birefringence dispersion curve in some known models describing polarization state of a collimated uniform beam after passing a birefringent non-image-forming system. By the use of a modified definition of the complex degree of coherence it is shown that the presence of birefringence dispersion is analytically equivalent to a transformation of the spectrum profile of the beam passing through a non-dispersive system. This remark is then utilized for error reduction in numerical calculations of depolarization in a system with a frequency dependent differential group delay when the power spectrum density is given in discretized form. The same numerical technique applies both for implementations of coherence-based solutions and for the Mueller-Stokes formalism with polychromatic illumination, without imposing any restrictions on the power spectrum shape or width.

Fast adaptive bidimensional empirical mode decomposition (FABEMD) is a data-driven image processing method that decomposes 2D signal into a set of bidimensional intrinsic mode functions (BIMFs) and residue via sifting process. FABEMD was recently reported as a promising tool for moiré fringe pattern analysis. In this contribution we propose a modified FABEMD method for extraction of micro and macrostructures present in incoherent superimpositions of both cosinusoidal and binary gratings. A new structure with unique properties is pointed out. One can create it by subtracting the additive moiré pattern from the multiplicative one. The resulting structure consists of a sum of two information carrying (the difference and sum beat frequencies) components easily separable using the FABEMD method. In the case of the so-called digital moiré where one has an access to both gratings (specimen and reference). One can rescale their intensity ranges to [-1,+1] and superimpose them multiplicatively giving rise to a similar structure as obtained by above mentioned subtraction. Numerical studies confirm great potential of the FABEMD method in supporting the space domain interpretation of incoherent moiré superimpositions.

In this paper we present a new method for the fringe pattern separation. Our method is useful when two fringe families are present in a single image, either in case when two of them carry an encoded information (e.g., three beam interference encountered in wedge or quasi-parallel plate testing), or when one pattern carries an information and the other one is parasitic and to be removed. The method is based on the two dimensional continuous wavelet transform and the modified Morlet wavelet. A new ridge extraction algorithm is proposed to deal with multiple fringe families. The validity and accuracy of the proposed method is confirmed by computer simulations.

We present a new method for the measurement of a residual birefringence in a polariscopic interferometer. Measured medium inserted into the setup can cause the changes in the polarization state of the propagated beam. Specific orientation of the elements (i.e. the analyzer and the phase retarder) modifies the setup response to the small changes of the azimuth and ellipticity angles of the propagated beam - the sensitivity of the setup is highly increased within the limited measuring range. The sensitivity and the measuring range of the setup can be adjusted by proper mutual orientation of the setup elements. Even though the measurement requires the analysis of the low contrast interferograms, what can be difficult, the application of the Fourier analysis allows the calculations for the interferogram contrast lower than in case of classical interference pattern shift tracking. In the present paper both theoretical considerations and experimental results taken from the experimental model setup are presented. Hundredfold increase in sensitivity was obtained in the presented experiments, which allowed the measurement of phase difference introduced by the birefringent medium with an accuracy of one hundredth degree.

Determination of the interference phase, i.e. the mutual phase shift between interfering waves is a principal issue in the interferometric measurement, especially on the nanometre scale. Our goal was to develop a novel interference phase detection technique that employs a computational approach and a frequency modulation of the laser source to achieve comparable performance with a homodyne detection with an optical phase shift generation. We have used a Michelson setup with polarizing optics that allowed to compare both the homodyne detection method and our novel method side by side while both methods shared the optical setup. Our method also comprises error compensation that deals e.g. with residual amplitude modulation and the scale non-linearities. The experiments revealed that the novel method achieves a periodic error less than 0.16 angular degrees and a standard deviation of less than 1.5 degrees, compared against the reference. The operational distance was 600mm. The method had proven it is suitable replacement for traditional homodyne detection techniques since it has comparable performance and significantly lower demands on the optical setup.

A holographic recording utilizing a multimode light source – laser diode module, is analyzed. The analysis results in a simple experimental method enabling to determine the frequency shift of longitudinal laser diode module modes. Moreover, the analysis provides with a possibility to avoid the moiré structure of holographic recording in a degree. The results can be used to evaluate the time coherence of LDM, and in the frame of educational process (e.g. students specialized in photonics), too.

A new self-developing recording material with silver bromide nanoparticles and photopolymerization system has been prepared and tested as a recording medium for optical holography. Through the method of the real-time measurement of a diffraction grating growth, we have shown that an efficient volume phase grating is formed during a holographic exposure. The refractive index modulation of the formed grating is several times higher than in the case of standard acrylamide-based photopolymers with a similar composition. The material response on different exposure parameters has been measured and obtained results have been discussed. The transfer of nanoparticles within the recording layer, which is the main cause of the grating growth, has been experimentally verified through the direct observation of the grating micro-structure with the scanning electron microscope.

In this contribution the fractal speckle effect is simulated by means of a modification of the proposed numerical model of propagation of ordinary speckle effect. The modification is based on an illumination of a rough object surface by a diffractal – a wave diffracted on an amplitude fractal transparent. The correlation properties of simulated fractal speckle propagated in free space at various angles of observation are investigated with regard to a fractal dimension of the amplitude transparent.

White-light interferometry is an established and proved method for the measurement of the geometrical shape of objects. The advantage of white-light interferometry is that it is suitable for the measurement of the shape of objects with smooth as well as rough surface. The information about the longitudinal coordinate of the surface of the measured object is obtained from the white-light interferogram. The interferogram is the intensity at the detector expressed as the function of the position of the object. (The object is moved along the optical axis during the measurement process.) If the shape of an object with rough surface is measured, the phase of the interferogram is not evaluated because it is a random value. The information about the longitudinal coordinate is obtained from the center of the interferogram envelope. A classical method for the calculation of the envelope of white-light interferogram is the demodulation by means of Hilbert transform. However, the electric signal at the output of the camera is influenced by the noise. Therefore, as expected, the calculated envelope is also influenced by the noise. The result is that the measured longitudinal coordinate of the surface of the object is affected by an error. In our contribution, we look for the answer on following questions: How does the noise of the evaluated envelope differ from the noise of the interferogram? What is the minimal measurement uncertainty that can be achieved?

The behavior of four angular parameters describing polarization ellipse is analyzed in the vicinity of Poincare sphere poles. It is shown that the phenomenon of step-wise change of azimuthal angle of polarization ellipse at π/2 near poles s₃ = ±1 is not accompanied by discontinuities in other parameters of polarization ellipse. In particular the dual system of angular parameters “amplitude-ratio angle and phase difference” do not experience any discontinuities near the poles s₃ = ±1. The same is true for the area of polarization ellipse, which is shown to be continuous on the whole Poincare sphere. Analogously, step-wise change of phase difference at π near poles s₁ = ±1 is not accompanied by any discontinuities in basic system of angular parameters “azimuth-ellipticity”. General features of angular parameters behavior are illustrated by the results of numerical modelling.

This paper presents a novel principle for contactless gauge block measurement using a combination of low-coherence interferometry and laser interferometry. The experimental setup combines a Dowell interferometer and a Michelson interferometer to ensure a gauge block length determination with direct traceability to the primary length standard. This setup was designed for contactless complex gauge block analysis providing information about gauge block length, gauge block faces surface profile (e.g., indication of scratches) and by analysis of the interference fringes shape, also about the gauge block edge flatness distortion. The designed setup is supplemented by an automatic handling system designed for a set of 126 gauge blocks (0.5 mm to 100 mm) to allow the automatic contactless calibration of the complex gauge block set without a human operator.

We present a concept combining traditional displacement incremental interferometry with a tracking refractometer following the fluctuations of the refractive index of air. This concept is represented by an interferometric system of three Michelson-type interferometers where two are arranged in a counter-measuring configuration and the third one is set to measure the changes of the fixed length, here the measuring range of the overall displacement. In this configuration the two counter-measuring interferometers have identical beam paths with proportional parts of the overall one. The fixed interferometer with its geometrical length of the measuring beam linked to a mechanical reference made of a high thermal-stability material (Zerodur) operates as a tracking refractometer monitoring the atmospheric refractive index directly in the beam path of the displacement measuring interferometers. This principle has been demonstrated experimentally through a set of measurements in a temperature controlled environment under slowly changing refractive index of air in comparison with its indirect measurement through Edlen formula. With locking of the laser optical frequency to fixed value of the overall optical length the concept can operate as an interferometric system with compensation of the fluctuations of the refractive index of air.

The work presents measurements of the length stability of Zerodur glass ceramic with temperature change. Measurement of this thermal characteristic is necessary for determination of the optimal temperature at which the Zerodur glass ceramic has a coefficient of thermal expansion close to zero. The principle of the measurement is to monitor the length changes using an optical resonator with a cavity mirror spacer made from the Zerodur material to be studied. The resonator is placed inside a vacuum chamber with a temperature control. A tunable laser diode is locked to a certain optical mode of the resonator to monitor the optical frequency of this mode. A beat-note signal from optical mixing between the laser and a stabilized femtosecond frequency comb is detected and processed. The temperature dependence of the glass ceramics was determined and analyzed. The resolution of the length measurement of the experimental set-up is on the order of 0.1 nm.

The work presents a measurement of lengths by an optical measuring resonator. The resonator works as distance-to-optical frequency converter with ultimate linearity. It has locked a tunable laser to certain cavity mode. The optical frequency of the laser is heterodyned with immediate “tooth” of the femtosecond comb spectrum. For the testing of the method the special combination of the optical resonator and Michelson interferometer was put together. This system combines the cavity length of the optical resonator with the measuring arm of the Michelson laser interferometer. The one mirror of the system is common for both laser interferometers and it is driven by piezoelectric transducer. The testing range is limited by the range of tuneability of the used laser and it covers 1000 nm of the length measurement.

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f–2f ¹ technique and with fully digital servo-loop stabilization of the fs comb. Secondly, we are using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f– 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset and repetition frequencies of the fs comb.

Original matrix formulas obtained by differentiation of the system matrix in respect to movements of components are derived. Components kinematics for the three zoom systems realized by means of interactive graphical software is presented. An optical system may be structurally designed by successive steps and its parameters determined to fulfil requirements, such as optical conjugation, focal lengths or magnifications. Improved software developed in this work serves both determination of optical powers and separations and movements of components. Developed methodology covers different types of fixed and zoom systems, the latter type with electronic or optical compensation. One may consider any optical system, such as the reproduction lens, objective lens or telescope system, because matrix optics distinguishes them remarkably easy. Kinematics pertaining to a full tract of the zoom system is determined at a discrete number of positions. Movements of so-called basic variable components are determined in a full cycle of work by means of iterative methods while movements of supplementary components may be inserted by means of exponential-parabolic functions also including their linear form. Any component of the zoom system may act as a variable, supplementary or fixed component, but it is mainly dependent on the structural design. Parameters of characteristics are computed as elements of a certain matrix. Designing is that to set these elements on required values by means of system parameters or movements of components. In this way, one may create complex multi-group systems with characteristics and movements which we accept. Properties of these systems are presented by numerical and graphical forms. Advantages of these systems are their more compact construction, more smooth kinematics, and better possibilities of optimization, what is particularly valuable for zoom systems with a high zooming ratio.

The Geant4 toolkit is important and popular software for simulation of physics processes in various areas. In spite of its primary application in high-energy particle physics and astrophysics, it is also widely used for studies in space and medical science. The accuracy of Geant4 simulations depends on the credibility of both models of physics processes and the description of materials involved in simulations. In this work, model of rough isotropic optical surfaces is extended to Geant4 providing with the knowledge of their in-plane BRDF scatter profile. We updated Geant4’s algorithm responsible for tracking photon on a boundary of two optical environments to reflect the scatter profile of isotropic optical surfaces. To examine reliability of models, we measured BRDF profile of Tyvek, mylar and glass mirror samples by means of CASI measurement systems. We used obtained BRDF profile to setup optical properties of model counterpart of measured samples. Then we compared scattered profile in simulation with real one.

Nowadays, in the field of communications systems radio transmission frequencies are dominant inside buildings. Due to the increasing of large number of users and devices, that use these frequencies, there is danger of accruing interferences and reducing the transmission performance. Therefore, indoor wireless optical systems are beginning to use as an alternative solution. Indoor wireless optical systems can use for communication direct and reflected light rays. This article deals with the measurement of optical power distribution in the model dark room. As a light source we use white power LEDs located on the ceiling of the room. The measurement of the optical power distribution was performed in dark room, which was specially constructed for this purpose. This room was also modelled in LightTools software that allows simulate a real measurement. This article compares the results of the measurement and the simulation.

The free space optic links are used in places, where it is very difficult to use optical fiber links. The advantages of free space optic link are a great bit rate, easy and fast installation, unlicensed frequency band. The greatest disadvantage is transmission medium, which it uses in case of FSO link, the atmosphere. The worst influence on FSO link is caused by atmospherical effect called fog. This article deals with the study of fog influence on FSO link and its bit error ratio. The real measurement of BER with artificial generated fog and FSO link was performed. The measurement was done in laboratory conditions. The results are presented in this article.

ABSTRACT Synthetic diffractive structures represent an important tool in the optical document security. Their macroscopic visual behavior is based on properties of a very fine micro-structure which cannot be copied using common copying techniques. The visual effects can be easily observed by a common observer without any special inspection tools. However, when a high level of security is needed, additional features are often included based on an optical encryption of information. In this paper, a novel encryption technique is presented, which is based on utilizing the plastic holographic foil as a waveguide and special diffractive structures as coupling elements. When an in-coupling area is illuminated with a defined light beam, the light is coupled into the waveguide and travels to an out-coupling part. The encrypted information is encoded either in the shape of the out-coupling area or it can be formed from an out-coupling hologram in free space above the element. Both laser and normal white light sources can be used for reading the information. The coupling areas can be mixed with diffractive micro-structures forming visual effects and can be invisible during a normal observation of the hologram. The couplers can be realized using the technology fully compatible with the standard process for mastering and replication of the security elements. Several extensions of the described idea of waveguide cryptograms are also included. Finally, a set of real samples of the security elements is presented, which were realized using an advanced matrix laser lithography technique.

The control of burners is a key issue for a stable and smooth sintering process. A special image processing tool (the thermography function by means of technical boroscope) offers the method of such measuring. The main idea of all these systems is to document the continuous changes of the sintering process by a color (state-of-the-art) camera. For real-time processing video signals a Vision Acquisition Software from National Instrument can be used, it allows a cooperation with interface USB 2.0 and FireWire (IEEE1394). The converter ADVC-100 from CANOPUS may be used for signal conversion from analog cameras PAL-NTSC. Using stable computer programs, e.g. functions of technology Remote Panels NI (National Instruments), the combustion process can be monitored and controlled via web browser, phone or SmartPhone.

Intraocular lens (IOL) is an artificial implant substituting natural crystalline lens which is non-transparent due to cataract. Incorrect location of the IOL in the eyeball (e.g. its shift or tilt) causes significant deterioration of patient’s vision. The analysis of Purkinje images (i.e. reflections from successive refracting surfaces in the eye) enables to determine the real IOL location and thus helps in evaluating the retinal image quality. The experimental setup for Purkinje images recording consists of illuminator, composed of a number of infrared LEDs, telecentric lens and detector (CCD camera). Analysis of mutual position of particular reflections enables to evaluate the lens location in respect to the corneal axis. The actual measurements are realized on artificial eye model, what allows to estimate the precision of the algorithm applied in the calculations. In the future the experimental set-up will be adapted to measure the eyes of real patients.

Paper presents method of numerical analysis of time variability the eye pupil geometry by use of the first and the second moments of irregular pupil form. Sequences of the pupil shape variations were recorded by use of high-speed CCD camera, with recording speed 250fps and next analyzed on a group of 11 patients. The shape of the pupil for each frame from the sequence was characterized numerically by use of second moments of inertia and orientation of its principal axes. Additionally the area and coordinates of center of gravity of the pupil were calculated. Kinetics of the pupil area, its moment of inertia and principal axes inclination angle were analyzed for each sequence. Results of calculations based on the real shape of the pupil were compared with the elliptic approximation of the pupil form. Calculations show high similarity of results for elliptic approximation of the pupil form and the real form approach. However, more exact analysis show a clear differences in the variability of pupil parameters.

Spiral phase contrast imaging is one of the modern methods of optical microscopy applicable to edge contrast enhancement of amplitude and phase samples. The method is based on a spatial spectrum filtering realized by a spiral phase element at the focal plane of the Fourier lens. In this paper, the results of a paraxial wave model of the spiral imaging are presented which allow to calculate the point spread function for real parameters of the spiral filtering and to analyze defocusing effects. A particular attention is given to the analysis of the spiral imaging implemented by a phase mask with a finite number of discrete phase levels. As the main result, a defocusing-induced rotation of the point spread function is discovered and analyzed in detail. Theoretical predictions are verified in experiments using a spatial light modulator for generation of the discrete spiral phase mask.

Optical force acting upon a dielectric microparticle illuminated by a non-di racting vortex beam is expressed using the Generalized Lorenz-Mie theory (GLMT). Numerical results are presented for di erent widths and topological charges of the vortex beam. We show that such particle may be stably trapped either in the dark center of the vortex beam, in one of two stable positions placed o the optical axis, and as the third option it may circulate along almost circular trajectory having its radius smaller or equal to the radius of the smallest high intensity vortex ring.

In this contribution we focus on the heating and optical forces and acting upon a core-shell particles confined in a standing-wave. The considered spheres are composed either of gold or silver layer on top of a polystyrene core. We present the results of a computational study in which we modify the geometrical parameters of the particles and the wavelength of the trapping beams. This study may suggest optimal particle composition that may be utilized as an optically trapped probe for the surface enhanced Raman spectroscopy (SERS) of biomolecules.

The self-arrangement of several micron-sized particles (due to their mutual scattering of light fields) is called optical binding. The scattered light is induced by incident laser fields which may be also used for partial localization (similarly to optical tweezers) of the particles in the water solution. We have previously experimentally studied the optical binding in the configurations employing two counter-propagation Bessel beams and these results were sufficiently supported by our numerical simulations (Coupled dipole method { CDM). Here we present numerical studies of configurations where some symmetries of the problem are broken. We study how the difference of sizes of two spherical particles influences their spatial stable separation. These results may serve for detection of particles of different composition, size or shape.

Optical binding presents an original method for self- arrangement of solid microparticles in liquid or air. The resulting equilibrium positions of the particles in an optically bound structure (OBS) are not only influenced by the spatial intensity profiles of the incident laser beams but also by the light scattered from all the bound particles. The inter-particle distances in OBSs can be externally modified by changing the refractive index of the medium or the spatial intensity distribution of the beams. Especially the last option is now well developed due to the technology of spatial light modulators (SLM). We utilized this tool to generate OBSs in counterpropagating laser beams having various spatial intensity profiles. In contrast to the previous methods, where OBSs were kept stationary without dynamic control, we modified dynamically the optical cage for self-arranged particles which led to enlargement or shrinking of the OBS. Using elaborate optical fields suitable for particular cases we demonstrated the size tunability of OBSs that were self-arranged along one, two or three dimensions. Compressing of the optical cage below a certain limit led to a collapse of the self-arranged micro-structures, thus indicating a phase transitions in such colloidal structures. Within a system of counter-propagating optical vortices we observed transfer of angular momentum of light to two-dimensional OBSs, revolving around the intrinsic on-axis phase singularity of the trapping beams.

Optical interaction between particles known as optical binding lead to their self-arrangement in a motional array of optical traps created by interference of two counter-propagating and interfering evanescent waves. This configuration, also called optical conveyor belt (OCB), enables directed and controlled motion of many such particles arranged into a linear chain with well-separated distances between them. We have observed a significant increase in the delivery speed of the whole structure as the number of particles in the chain increased and we have also quantified the contributions to this speed enhancement coming from the optical and hydrodynamical interactions between the particles.

We have constructed a device for active optical manipulation and Raman spectral analysis in a microfluidic channel for efficient, nondestructive and contactless sorting of biological samples based on the Raman spectroscopic characteristics of living cells. In our previous work, we have linked such Raman spectral characteristics of microalgal lipid bodies with the unsaturation or carotene concentration via a calibration curve. As the sorting platform we have used a combination of fast galvano-optic laser steering system and specially designed microfluidic chips. We used X shaped channels with two input and output ports, and also several differently shaped variants. The steerable trapping laser beam was designed to move the cell to the specified locations and confine the cell for the time period needed for the analysis.

The stiffness of a single optical trap is a basic parameter of optical manipulators and detecting the displacement of trapped object belongs to fundamental measurements [1]. The trap stiffness can be determined by position measurements of oscillating (with high frequency) dielectric microsphere. Usually the signal is captured by simple detector like quadrant photodiode [2]. However, this method is hard to apply when working in multitrap mode, especially in case of holographic optical tweezers. In multitrap mode, widely used method is video image processing focused on determining the center of mass of an object [3]. In this contribution we present the method for position measurment based on video sequence analysis from fast camera. The position is obtained by correlating the video frame with templates of known positions of that object. This algorithm can work on several objects, finding their positions independently. It has also scalable accuracy up to sub-pixel level.

The main goal of our investigation is to use Raman tweezers technique so that the responce of Raman scattering on microorganisms suspended in liquid media (bacteria, algae and yeast cells in microfluidic chips) can be used to identify different species. The investigations presented here include identification of different bacteria strains (biofilm-positive and biofilm-negative) and yeast cells by using principal component analysis (PCA). The main driving force behind our investigation was a common problem in the clinical microbiology laboratory - how to distinguish between contaminant and invasive isolates. Invasive bacterial/yeast isolates can be assumed to form a biofilm, while isolates which do not form a biofilm can be treated as contaminant. Thus, the latter do not represent an important virulence factor.

Scanning vortex microscope is a system in which sample is scanned by a Gaussian beam carrying optical vortex. We report on a new method in which the sample is scanned by moving the optical vortex inside the focused beam spot. Figure 1 shows a scheme of the optical system. The vortex lens shift induces a precise nanometre shift of the vortex point (i.e. point where the phase is undetermined) inside the focused spot. When moving the vortex lens along a straight line vortex point goes along a straight line of much smaller size and different orientation. There is a specific distance between the focusing lens and sample plane at which optical vortex is highly sensitive on sample topography. In this special plane vortex point’s movement is perpendicular to the vortex lens’ shift. Moreover, the angle of vortex point’s trajectory changes in a very rapid way. In the paper we investigate the dynamics of the vortex shift induced by different setup parameters.

In materials engineering, we are often faced with a necessity to display the shape and morphology of studied surfaces. This is essential for surface evaluation of various components as well as for new materials research. Several imaging techniques are available for such purposes. One of the most appropriate of them is laser scanning confocal microscopy. The magnification range of this technique satisfies the needs of researchers working between the limits of conventional optical microscopes and scanning electron microscopes. It overcomes the limitations of optical microscopy by better lateral resolution, ability to control the depth of field and possibility of high-resolution 3D imaging of relatively thick samples. Compared to the more advanced (and more expensive) scanning electron microscopes, laser scanning confocal microscopy has no special requirement for the sample preparation and there is also no need to measure in vacuum. Particular examples of laser scanning confocal microscopy beneficial use are presented in this paper. Scratch track evaluation, diamonds tip control, Tyvek structure examination and measurement of surface characteristics of a wire saw cut on the glass are reported.

Digital holographic microscope (DHM) allows for imaging with a quantitative phase contrast. In this way it becomes an important instrument, a completely non-invasive tool for a contrast intravital observation of living cells and a cell drymass density distribution measurement. A serious drawback of current DHMs is highly coherent illumination which makes the lateral resolution worse and impairs the image quality by a coherence noise and a parasitic interference. An uncompromising solution to this problem can be found in the Leith concept of incoherent holography. An off-axis hologram can be formed with arbitrary degree of light coherence in systems equipped with an achromatic interferometer and thus the resolution and the image quality typical for an incoherent-light wide-field microscopy can be achieved. In addition, advanced imaging modes based on limited coherence can be utilized. The typical example is a coherence-gating effect which provides a finite axial resolution and makes DHM image similar to that of a confocal microscope. These possibilities were described theoretically using the formalism of three-dimensional coherent transfer functions and proved experimentally by the coherence-controlled holographic microscope which is DHM based on the Leith achromatic interferometer. Quantitative-phase-contrast imaging is demonstrated with incoherent light by the living cancer cells observation and their motility evaluation. The coherence-gating effect was proved by imaging of model samples through a scattering layer and living cells inside an opalescent medium.

Coherence Controlled Holographic Microscopy (CCHM) is a novel holographic technique for quantitative-phasecontrast (QPC) biological observations particularly of living cells. Owing to the ordinary (low coherence) illumination source, the CCHM images are of low noise, deprived of coherence noise (speckles) and the lateral resolution is improved by a factor of 2 compared to classic holographic microscopes. Long-lasting time-lapse experiments require elimination of the CCHM optical system instability in order to achieve precise QPC measurement and to maintain correct CCHM adjustment for its low-coherence operation. The critical part of CCHM is the interferometer, which is very sensitive to temperature fluctuations and air turbulences. The temperature stabilization of the whole microscope without air turbulences is therefore required to provide stability for long-term observations of living cells. Novel heated microscope box and stage designed and constructed for this purpose are described in the paper. The system maintains a constant temperature of both the microscope and of the sample set to 37 °C thus providing optimal living conditions for living human and animal cells. The system is completed with a novel flow-chamber for living-cells accommodation during observation. A service of the system to CCHM is demonstrated by a series of pictures of growing cells.

In this paper the theoretical description of the imaging process of a coherence-controlled holographic microscope (CCHM) is carried out for the case when the object beam is influenced by a scattering medium (a diffuser) present between an observed object and an objective lens of the microscope. The calculation is based on the decomposition of the diffuser transmission function into its frequency components. The complete holographic image is then computed as the superposition of holographic images for individual frequency components. The dependence of fundamental imaging characteristics on the coherence state of an illumination is demonstrated.

In this paper we demonstrate efficient operation of the actively mode-locked Nd:YAG laser operating at the wavelength of 1,06 μm in bounce geometry under quasi-continuous diode pumping. The laser output pulse train consisted of ~50 pulses (at FWHM) with the total energy of 90 μJ, energetic stability better than 2 %, and Gaussian beam profile was generated directly from the oscillator. The mean pulse duration was measured to be 160 ps at FWHM. This regime was compared with actively-passively mode locked operation using a semiconductor saturable absorber mirror as a passive mode-locking element. Stable generation of single Q-switched and mode-locked train was achieved. The number of pulses decreased to ~10 pulses (at FWHM) and whole train energy increased to 160 μJ. Single pulse duration was shorter than our detection system limit of ~76 ps. The output pulse train generation stability and timing jitter decrease down to 260 ns show the advantage of using the active stabilization in quasi-continuously diode-pumped passively mode-locked lasers.

In this work we have investigated diode pumped passively mode-locked Yb:YAG laser operation in quasi-continuous mode. The laser was end-pumped by 25W laser diode operating in pulse mode, with 2ms long pulse and repetition rate of 10Hz. The laser system was designed with X-shaped resonator. Several semiconductor saturable absorber mirrors (SESAMs) were tested. Temporal development of a pulse train in a transient regime before the stabilization of the pulse amplitude and duration was investigated. After the transient period at the beginning of generation of about 25μs, the amplitude and also duration of mode-locked pulses is stabilized. Without intracavity dispersion compensation pulses with duration of 1,37ps (assuming sech² shaped pulse) were generated with the spectral width of 1,61nm on the wavelength of 1,03μm and pulse energy of 4,5nJ. Autocorrelator trace and oscillogram confirm good reproducibility and stability of the laser operation.

This work is oriented towards investigation of displacement measurement uncertainty contribution of different laser sources that are suitable for powering multidimensional interferometric positioning system for local probe microscopy. Main aim of this work was to find a suitable laser source for this measuring system. Most common 633 nm He-Ne lasers were compared with 532 nm frequency-doubled Nd:YAGs of different construction (external cavity doubling, ring configuration laser). We investigated amplitude and frequency noise of several lasers intended for micro- and nano- CMMs (coordinate measurement machines) and compared their noise properties together with the aim to find the best option. Amplitude noise measurements were done directly with the help of low noise photodetector, frequency noise of tested lasers was measured by two approaches – first with the help of Fabry-Perot resonator, which was used as a frequency discriminator converting a frequency (phase) noise into the amplitude one and second directly with the help of interferometer – measuring of interferometric fringe signal and position evaluation – another type of frequency discriminator. Both frequency noise and also amplitude noise measurements were done simultaneously to have a chance to compare both approaches and results.

In this work we have studied fundamental passive and active parameters of new family of erbium and ytterbium doped zinc-silicate glasses with different doping concentration and ratio of erbium and ytterbium ions. Parameters as absorption coefficient, saturation of absorption, emission wavelength, fluorescence lifetime and up-conversion spectra were measured. The laser performance was studied in end-diode pumped configuration with hemispherical resonator. As an excitation source a 30W fiber coupled 975 nm laser diode in pulsed regime was used. Laser action was achieved with four different samples of zinc-silicate glasses on wavelengths ranging from 1540nm to 1570nm. The results were compared with the properties of commercially available phosphate glasses and previous zinc-silicate glass which have similar threshold energy corresponding to 3,3mJ and 3mJ respectively. Newly designed zinc-silicate glasses prepared under improved conditions showed substantially better optical and laser properties in comparison with the previously prepared samples.

Laser structuring is rapidly developing manufacturing technique for broad spectrum of industrial branches, e.g. aerospace, power engineering, tool- and mould making, and automotive. It enables to prepare work pieces and products with very fine micro structures achieving a far better degree of details than conventional structuring techniques like etching or eroding. However, the state of art in laser structuring shows a crucial deficit. Used systems contain no metrology setup to detect the shape geometry (depth and length) and contour accuracy during the process. Therefore, an innovative in-line metrology technique based on low coherence interferometry for laser structuring systems has been investigated and described in the paper. In this contribution we present our results in the research of wideband and highpower light sources for the proposed low-coherence interferometric measurement system. The system can be incorporated into a structuring workplace equipped with a Q-switched ytterbium-doped fiber laser at 1064 nm for material processing. In the paper we focus on two wideband sources for such a measurement system. The first source is based on a superluminescent diode and the second one is based on an amplified spontaneous emission in a double-clad ytterbium-doped fiber. An example of results measured with the proposed in-line metrology system is presented.

The linewidth of the emission spectrum and the mode-hop free tuning range of the wavelength are crucial parameters for laser sources in laser interferometry, especially absolute laser interferometry. At present time the DFB (Distributed FeedBack), laser diodes are the most suitable laser sources from semiconductor laser sources for using in laser interferometry. We present our set-up of the optical fiber based laser interferometer where these laser diodes can be used. The DFB laser diodes have narrow frequency linewidth, mode hop free tuning range up to 2 nm and sufficient optical power. In addition to the other types of laser diodes are available in the package with optical fiber at the output and the DFB laser diodes with 1541 nm wavelength has optical isolator inside. Unfortunately the DFB laser diodes with 760 nm wavelength have no optical isolator inside package. This induces a back reflection from the fiber connections at the output to the laser chip. Than the mode hop free tuning range is decreasing rapidly. We present our experience with adaptation of the DFB laser diodes to laser interferometer and methods to decrease back reflection.

The development of high energy and high power lasers based on solid state technology is mostly limited by thermal effects that occur inside the laser cavity under high heat loads and intensities. The thermo-optical effects emerging inside cavity mirrors, output couplers and windows can significantly degrade beam quality of such lasers. The knowledge on transient thermal effects occurring inside bulk laser elements exposed on laser intensities of several dozens of kW/cm2 is of special interest for some specific applications (e.g. heat capacity lasers). The goal of this paper were theoretical analysis and experimental verification of these effects. Tips for best materials choice for cavity mirrors, laser windows and output couplers were shown. Simple theoretical thermo-optical model was presented. The special laboratory setup allowing simultaneous registration of thermo-optical effects applying shearing interferometer and wavefront sensor (Shack-Hartmann test) was elaborated. The non-stationary and stationary thermo-optical effects emerging inside tested mirrors can be observed, be measured and resolved as result of surface absorption in coating layers and volume absorption in the material. The resolution of measurements: less than 0.1 K and thermally induced optical power of about 0.1 D were demonstrated.

In this contribution we present a technology for deposition and testing of interference coatings for optical components designed to operate in power pulsed lasers. The aim of the technology is to prepare components for high power laser facilities such as ELI (Extreme Light Infrastructure) or HiLASE. ELI is a part of the Eropean plan to build a new generation of large research facilities selected by the the Eropean Strategy Forum for Research Infrastructures (ESFRI). These facilities rely on the use of diode pumped solid state lasers (DPSSL). The choice of the material or the lasers' optical components is critical. Some of the most important properties include the ability to be antireflection and high reflection coated to reduce the energy losses and increase the overall efficiency. As large amounts of hear need to be dissipated during laser operation, cryogenic cooling is necessary. The conducted experiments served as preliminary tests of laser damage threshold measurement methodology that we plan to use in the future. We designed a special apparatus consistion of a vacuum chamber an a cooling system. The samples were placed into the vacuum chamber which was evacuated and them the samples were cooled down to approximately 120K and illuminated by a pulsed laser. Pulse duration was in the nanosecond region. Multiple test sites on the sample's surface were used for different laser pulse energies. We used optical and electron microscopy and spectrophotometer measurements for coating investigation after the conducted experiments.

Research of the optical radiation interaction with human tooth tissues has started early after the first laser construction. Absorptivity of the particular tissue is dependent on the wavelength, thus CO₂, Er:YAG and Nd:YAG lasers were used in many experimental works all over the world. Near infrared radiation of the pulsed Nd:YAG laser was found to be suitable for dentine hypersensitivity treatment by sealing of the open tubules with melted and re-solidified dentin. Series of experiments were performed to find suitable process parameters in the laser laboratory equipped with the industrial pulsed Nd:YAG laser system. Tooth samples were prepared and classified into five groups according to their different degree of the surface grinding and polishing. Two types of antireflective agents, erythrosine and black ink, were applied on the samples surfaces. Coated samples and reference ones without any agents were treated with a set of increasing pulse energy values. Pulse frequency, pulse length, laser beam diameter on the sample surface and relative speed remained constant. Lines of the melted spots were displayed by confocal microscope; surface profiles were scanned by contact profilometer. Dimensions of the dentine melted spots were extracted from the measured data and their dependence on the laser pulse energy, degree of the surface grinding and type of antireflective agent were evaluated.

In this paper, the strain sensitivity of a two-mode birefringent holey fiber is measured in the spectral domain. In a simple experimental setup comprising a broadband source, a polarizer, a two-mode birefringent holey fiber under varied elongations, an analyzer and a compact spectrometer, the spectral interferograms are resolved. These are characterized by a specific wavelength, the equalization wavelength, at which spectral interference fringes have the highest visibility (the largest period) due to the zero group optical path difference between the fundamental, the LP01 mode and the higher-order, the LP11 mode. The spectral interferograms with the equalization wavelength are processed by a new method to retrieve the phase as a function of the wavelength. From the retrieved phase functions corresponding to different elongations of a two-mode birefringent holey fiber under test, the spectral strain sensitivity is obtained. Using this approach, the intermodal spectral strain sensitivity was measured for two orthogonal (x and y) polarizations.

In this paper a simple spectral interferometric method for precise determination of the zero-dispersion wavelength of fiber polarization modes using a supercontinuum source is presented. This technique is based on processing a single spectral interferogram recorded in an experimental setup utilizing a dispersion balanced Mach-Zehnder interferometer with a birefringent fiber under test, a supercontinuum source and a low-resolution spectrometer. The zero-dispersion wavelengths retrieved from the sigle interferograms are compared with those obtained by a wide spectral range measurement technique applied in the same setup, and good agreement between the results is confirmed.

In this report, the results of theoretical analyses on the light guidance in the microstructured fibers infiltrated with liquid crystalline materials are presented. More precisely, the analyzed photonic structure is considered as 2D optical lattice (i.e., matrix of the mutually parallel waveguide channels) allowing thus the light to be switched (tunneled) between adjacent channels, as predicted by the series of the numerical simulations performed. The latter are based on the finite difference beam propagation method with the Crank-Nicholson scheme applied. It has been demonstrated that different scenarios for discrete light propagation can be obtained, depending on the internal and external factors governing geometrical and optical properties of both the light beam and the fiber. Our findings pave the way for all-optical switching to be successfully developed in the future practical photonic devices.

To achieve high non-linearity in photonic crystal fibers a high nonlinear coefficient of the glass is required accompanied by high coupling efficiency and flat dispersion profile of the fiber with the specific zero dispersion wavelength. In this paper, we present a deterministic method that allow step-by-step design of photonic crystal fibers with desired zero dispersion wavelength, modality and coupling efficiency due to sequential engineering of geometrical parameters of microstructured fibers with nanostructured cores. The fiber consists of inclusions of low refractive index material, embedded in a host glass of higher refractive index, where a single central micro-rod is omitted. In its place an additional nano-inclusion is located of a given diameter. The choice of the glass determines the nonlinear coefficient of the fiber and fabrication possibilities as well. Zero dispersion wavelength is varied by the change of the lattice constant of the cladding. High filling factor in the cladding leads to a large number of propagating high order modes, which can be selectively cut off, when the filling factor of the outer part of the cladding is reduced. The diameter of the nano-inclusion in the core is responsible for the fundamental mode area, which influences directly the coupling efficiency. Several designed structures were modeled numerically and developed to confirm the design method.

In this study, several approaches to optical switching in multiple core nonlinear microstructured optical fibers are presented. All approaches are based on coupling between the cores of a fiber. Based on Kerr effect, coupling is tuned and detuned by the switching signal. The propagation constants and field distributions are calculated using our in-house fullvectorial finite element mode solver. Copropagation of the signals at the switching and data wavelengths in a multiple core microstructured optical fiber is analyzed using the finite element beam propagation method and coupled mode theory. The crucial factor for successful implementation is the fabrication tolerance. Therefore, the dependence of the coupling efficiency on geometry tolerances is also analyzed. From these inaccuracies, the necessary coupling strength and consequently the switching power are deduced. It is shown that for an accuracy of about 2%, the necessary switching power is approximately 26 W in chalcogenide glass fibers.

We present our first basic concept of the simulation of stimulated Brillouin scattering (SBS) in this paper. We summarize basic theories of SBS in standard communication optical fibers. We are using the simulation to recognize effects of using SBS to generate acoustic waves in fibers. The acoustic waves in the optical fibers can be used to create long period fiber grating. We present our application of this effect in our concept of fiber spectrometer and optical filters. Basic principle of these applications is in the interaction of acoustic waves with measured laser beam in the optical fiber. The interaction of acoustic waves and the measured laser beam in the optical fiber is demonstrated.

We present results on the development of signal sources for the 2000 nm band. The ASE source is presented with a FWHM bandwidth of 70 nm and -20dB bandwidth of 229 nm with an integrated power of 7.5 mW. Narrow band lasers are presented made of a short piece of core-pumped thulium doped fiber and fiber Bragg gratings. High power lasers were constructed of double clad fiber. The low reflective output mirror was formed of the fiber loop. Highly reflective wideband mirror was used in a free running laser while fiber Bragg grating was used in a high-power all-fiber narrowband laser.

We present an experimental study of nonreciprocal ring laser, which can be operated without any isolator. While linear non-magneto-optical components manifest reciprocal behavior, reciprocity can be broken in nonlinear elements. Here we present the nonreciprocal ring laser with a fiber loop mirror. This turns the laser into a device with single output port only, so that no energy is wasted. Measurement of clock-wise and counter-clock-wise power in the ring cavity of laser indicates pronounced unidirectionality of the power inside the active fiber ring. Counter-clock-wise component was suppressed by 17.5 dB with respect to the clock-wise component. The configuration may be used at wavelengths and/or powers, where isolators are not easily available.

Fiber lasers have been extensively studied thanks to their high output power, excellent characteristics of output beam, relative simplicity, reliability and other promising features. In the paper we present a numerical model of all-fiber passively Q-switched laser and experimental observations of Q-switched pulsed regime in all-fiber laser. Numerical model is based on finite difference method and enables to investigate various spatial and material configurations of both active and passive fibers used in the laser cavity. Different laser regimes (pulsed and continuous-wave) can be achieved by selection of proper input parameters. Numerical model enables us to evaluate optical power and population level distributions in spatial and time domain. Experimental realization of passively Q-switched fiber laser was verified using the laser setup consisting of Er-Yb co-doped active fiber and Tm-doped fiber as saturable absorber. Q-switched regime was observed out in linear (Fabry-Perot) configuration with 3 nm wide tunable bandpass filter (TBPF) for adjustment of spectral position of the Q-switched laser output wavelength.

We report laser line self-sweeping phenomenon in rare-earth doped fiber lasers. The effect of self-sweeping is observed in erbium-doped fiber laser and also in the ytterbium-doped one. The former, having linear layout, is core-pumped by laser diode (LD) at 980 nm. Laser cavity is formed with fiber loop mirror and angle cleaved fiber end. Laser operation is delimited by tunable filter; we observed sweeping regime in 0.5 nm wide interval defined by the filter. Yb-doped allfiber laser has linear layout as well. Laser is cladding-pumped by LD at about 976 nm; cavity is constrained by rightangle cleaved fibers. We observed laser line sweeping having a range of 6 – 8 nm. We characterized both lasers with respect to sweeping properties thoroughly. We present output laser line wavelength and instant output intensity versus time; we show dependence of sweeping range, sweeping rate, and sweeping period on output laser power and pump laser temperature (pump laser wavelength).

A model of surface plasmon resonance fiber optic sensor operated in spectral domain is presented. The sensing scheme is based on a multimode optical fiber whose core is covered by thin silver film. Theoretical description of the proposed fiber optic structure is carried out in the frame of multilayer optic approximation. For the sake of clarity, the excitation by collimated centro-symmetric beam focused on the sensing fiber axis is supposed and only the propagation of meridional rays is considered. The contribution of s and p-polarization is included in the computation, however only p-polarization is affected by surface plasmon resonance phenomenon. The optical dispersion of all involved materials is taken into account. It is known that the usage of silver surface plasmon resonance detection layer leads to narrower dip (comparing to gold layer) and higher sensitivity, but the chemical stability of silver is the potential problem. The solution to this problem can be the creation of oxide overlayer on the top of the surface plasmon resonance detection layer. The effect of the overlayer thickness on the performance of the sensor is analyzed in detail using numerical simulation and discussed in terms of sensitivity and detection accuracy.

The interferometers composed of optical fibers are due to its high sensitivity capable of to measure various influences affecting the fiber. These influences may be bending or different sorts of fiber deformations, vibration, temperature, etc. In this case the vibration is the measured quantity, which is evaluated by analyzing the interference fringes representing changes in the fiber. Was used a Mach-Zehnder interferometer composed of the polarization maintaining elements. The polarization maintaining elements were used because of high sensitivity to polarization state inside the interferometer. The light was splitted into the two optical paths, where the first one is the reference fiber and it is separated from the actual phenomenon, and the second one is measuring fiber, which is directly exposed to vibration transmission from the underlying surface. The light source was narrowband DFB laser serating at a wavelength of 1550nm and as a detector an InGaAs PIN photodiode were used in this measurement. The electrical signal from the photodiode was amplified and fed into the measuring card. On the incoming signal the FFT was applied, which performs the transformation into the frequency domain and the results were further evaluated by software. We were evaluating the characteristic frequencies and their amplitude ratios. The frequency responses are unique for a given phenomenon, thus it is possible to identify recurring events by the characteristic frequencies and their amplitude ratios. The frequency range was limited by the properties of the used speaker, by the frequency characteristics of the filter in the amplifier and used resonant element. For the experiment evaluation the repeated impact of the various spherical objects on the surface board was performed and measured. The stability of amplitude and frequency and also the frequency range was verified in this measurement.

The Fiber Bragg Grating (FBG) sensors are nowadays used in many applications. Thanks to its quite big sensitivity to a surrounding environment, they can be used for sensing of temperature, strain, vibration or pressure. A fiber Bragg grating vibration sensor, which is interrogated by a distributed feedback laser diode (DFB) is demonstrated in this article. The system is based on the intensity modulation of the narrow spectral bandwidth of the DFB laser, when the reflection spectrum of the FBG sensor is shifted due to the strain that is applied on it in form of vibrations caused by acoustic wave pressure from loud speaker. The sensor’s response in frequency domain and strain is measured; also the factor of sensor pre-strain impact on its sensitivity is discussed.

Continuous casting is a modern and advanced technology of steel production, which product is a blank as an intermediate product for further processing. One of the most important parts of this whole process is crystallizer. At present most of methods, describing how to analyze the temperature profile of crystallizer in operation, were published and experimentally verified. These methods include the use of thermocouples or Bragg’s grids. New sophisticated method of analysis of crystallizer temperature profile is the use of optical fiber DTS based on stimulated Raman dispersion. This paper contains the first experimental measurement and method’s verification, which are necessary for the deployment this method into industrial practice.

Nowadays, it is obvious that the access networks will be build up from optical networks. With that are linked also optical components. These components are mostly passive connectors and splitters. In terms of the attenuation budget of the entire network, especially the splitters are very important elements in planning of the networks. The change in attenuation of these elements can lead to failure of the entire network. This article is focused to the issue of measurement of attenuation changes of the fiber optic splitters caused by the temperature with different dividing ratios and number of branches. The article describes the attenuation changes with temperature for commercially available single-mode fiber optical splitters and its capabilities for internal use. Effects of temperature were simulated in specialized chamber, which can reach the temperatures of value about 300 °C. Each fiber splitter was measured from all directions and several times in order to construct the statistical evaluation of the measured and calculated data. The measurement content also included determination of attenuation, crosstalk between the branches, insertion loss and total loss.

We report on a design for integrated surface diffraction grating fiber to chip coupler designed on Silicon-on-insulator platform with subwavelength grating, which is compatible with 193 nm laser DUV lithography. Surface diffraction grating couplers are perspective coupling solution, which extracts light from the Silicon-on-insulator wire waveguide and emits it towards an optical fiber placed over the SOI chip¹. However, they are polarization and spectral sensitive. Efficient grating-to-fiber coupling requires matching the grating radiated field profile and the optical fiber mode. The aim of this design is the reducing back reflection of the fiber to chip coupler by using subwavelength grating for continuously tuning effective refractive index and tune the profile of diffracted power. The structure of designed fiber to chip coupler consists of relatively large tapered segment which adjusts cross-section of SOI wire waveguide to standard single mode fiber diameter and surface diffraction grating for vertical coupling to the fiber. The simulation of the fiber to chip coupler is performed by FDTD tool and BPM tool. The effective refractive index is tuned over diffraction grating by adjusting the duty cycle of the silicon in subwavelength grating inside the surface diffraction grating.

Future development of optical access technologies expects increasing traffic and bandwidth. The first candidates to improve Gigabit-capable passive optical networks (GPON) are 10-Gigabit-PON (XG-PON) and wavelength-division multiplexing PON (WDM PON). Another possibility for increasing penetration of current PON branch is to extend number of channels provided on one optical fiber for one PON technology. Coexistence of GPON, XG-PON and WDM-PON in the same infrastructure is a most discussed issue concerning passive optical networks nowadays. Therefore, extensive studies are necessary to design proper and low-cost candidates. International Telecommunication Union (ITU) allocates specific wavelength bands for the present status quo and the future development of access technologies. However, within coexistence, it is necessary to protect signals from various PON technologies from interference. A potential barrier to deploying XG-GPONs and WDM PONs with current GPONs is the usage of broadband light sources and sophisticated optical methods of slicing the light source emission into specific wavelength channels. Protective measures comprise the exact allocation of upstream and downstream signal bands for each technology; the so-called guard bands within the wavelength allocation scheme to protect signals; and optionally the usage of wavelength blocking filters. In this contribution, bandpass thin-film filters are numerically presented for hybrid time division/wavelength division multiplexing TDM/WDM (TWDM) and for simple operation. They have been designed to be tunable and as steep as possible to reject the wavelength bands outside those allocated to TWDM-PON. The TWDM-PON filters are proposed to guarantee steep transmission curves in the vicinity of cut-on/cut-off wavelengths of the specific allocated wavelength bands and facilitate migration from legacy GPON and XG-PON to TWDM-PON. Their deployment protects the allocated wavelength bands from the undesirable interference.

The optical access networks are nowadays swiftly developing in the telecommunications field. These networks can provide higher data transfer rates, and have great potential to the future in terms of transmission possibilities. Many local internet providers responded to these facts and began gradually installing optical access networks into their originally built networks, mostly based on wireless communication. This allowed enlargement of possibilities for end-users in terms of high data rates and also new services such as Triple play, IPTV (Internet Protocol television) etc. However, with this expansion and building-up is also related the potential of reach in case of these networks. Big cities, such as Prague, Brno, Ostrava or Olomouc cannot be simply covered, because of their sizes and also because of their internal regulations given by various organizations in each city. Standard logical and also physical reach of EPON (IEEE 802.3ah - Ethernet Passive Optical Network) optical access network is about 20 km. However, for networks based on Wavelength Division Multiplex the reach can be up to 80 km, if the optical-fiber amplifier is inserted into the network. This article deals with simulation of different types of amplifiers for WDM-PON (Wavelength Division Multiplexing-Passive Optical Network) network in software application Optiwave OptiSystem and than are the values from the application and from real measurement compared.

On the present time, the most used technology of core networks is Wavelength-division multiplexing (WDM) which save a lot of bandwidth of optical fiber. But in each node all optical signals must be converted into the electrical domain, processed and converted back into the optical domain. Result of all these steps is that the data spend in the node a lot of time. This time decreases total available bandwidth in the optical networks. One of the results is that we compose WDM nodes which represent hybrid system of switching and controlling. If we use out-of-band signalizing it is simpler to separate control head from the data. For effective control and transmission of data over the optical networks, the reservation protocols are needed in WDM/OBS4,5. In today’s networks exist a lot of the protocols, which have their own advantages and disadvantages. For our investigation it was chosen the reservation protocol called Search & Compare (S &C)1, because it uses parallel-segment based and parallel link reservation. The structure of data will be designed from the point of view of wavelength for transmission channels, length of optical burst, source and group addresses in the segment, number of nodes and the total time needed for switching. Structure of the protocol will contain all of the control messages which are necessary for reservation a path along all segments. The design of the protocol follows the ITU-T recommendation2,3.

The paper is devoted to Au/Fe/Au/glass and Au/Fe/glass structures intended as MO SPR sensor units. The model approach based on matrix algebra is used to describe the response of discussed structures to external magnetic field. The theoretical results are confirmed by experiments realized by Multiscope device. The attention has been focused on a sensitivity of proposed response factors ρ^±(Φ) and F to magneto-optical effects. The application of ρ^±(Φ) response factor for our structures description is limited. The F factor has practically linear character such as change of external magnetic field and ferromagnetic thin film thickness.

Metamaterials (MM) represent a class of artificially-made structures, exhibiting, if properly designed, negative values of effective permittivity and permeability in specific spectral regions simultaneously. Recently, such structures have indeed attracted much attention due to their unique optical behavior not found in nature. These structures offer, e.g. a possibility of practical realization of perfect lenses, possessing a spatial resolution below the wavelength limit. In this contribution, we have focused on theoretical rigorous study on one specific class of MM structures, called fishnets, consisting of a combination of metal and dielectric layers with periodically arranged sub-wavelength holes. Our attempt was to reveal the physics and optimize the fishnet structure by tailoring the geometrical features in order to achieve optimized response in terms of negative refraction indices in particular spectral regions. For that purpose, our in-house 2D rigorous coupled wave analysis (RCWA) software was used for rigorous computing, the results of which were afterwards post-processed in order to retrieve the effective parameters. Using this tool, with the help of our approximate model, enabling more physical insight of wave-coupling processes, numerical simulations of plane-wave excitation of the multilayered nanofishnets have thus been performed. The reflection and transmission coefficients have been calculated and the effective material parameters have consequently been extracted from the obtained data, via the homogenization procedure.

Three dimensional (3D) Fourier modal methods, namely aperiodic rigorous coupled wave analysis (aRCWA) and the 3D bi-directional mode expansion and propagation method (BX3) have been recently developed and applied as the efficient and robust frequency-domain simulation tools for modeling both modal and propagation characteristics of advanced photonic and plasmonic nanostructures. In this paper, particularly, after a brief review of types of plasmonic waveguides, we report on several novel types of 3D plasmonic waveguides, especially those of the dielectric-loaded surface-plasmon waveguide (DLSPW) type. In particular, such novel types as hybrid guides, call hybrid dielectric plasmonic slot waveguides (HDPSW), being able to effectively combine strong field confinement with reasonable propagation lengths, are presented and discussed, based on the results of our numerical 3D simulations, in terms of geometrical dispersions, propagation characteristics, and the trade-offs between losses and localization. Using our methods, optical properties of various configurations of such waveguide structures have been numerically analyzed, confirming that these elementary structures represent very promising building blocks for future advanced functioning plasmonic devices.

Photonic crystals (PhC) are very interesting periodic material entities with many attractive physical properties. Moreover opaline-based PhC represent very simple way of realization of these PhC. In this contribution, we present our recent studies on both modeling and realization of these opaline based PhC (primarily based on SiO₂). Presented opals were prepared by self-assembly method based on the modification of a simple sedimentation technique. This alternation represented the spatial restriction of space region where the opal was constructed. Even more interesting properties, including the presence of the band gap, can be revealed via infiltrated and / or inverse opals. We have chosen photoconductive poly(9-vinylcarbazole) (PVK) as the material for infiltration and final inversion procedure. We have produced highly regular opals and stable inverse opals. Numerical modeling of these opaline structures has been carried out with the use of both MPB (simulations of simple and infiltrated PhC) and Meep tools (simulations of PhC in inverse configuration with the dispersion of PVK taken in account).

New approach for reducing of the dimensions of Y-branch optical power splitter by using a two-dimensional photonic crystal (PhC) is reported in this paper. Two-dimensional photonic crystal with photonic band gap was designed and simulated by plane wave expansion algorithm (PWE). This optical power splitter was designed for 1.31 μm wavelength range and it is based on AlxGax-1As/GaAs material platform. Optical power splitter was designed by RSoft's Photonic Component Design Suite and 3D simulations were performed by beam propagation method (BPM). The PhC implementation with suitable pattern in to Y-branch optical power splitter leads to spread the optical signal on it. It results in sharper division and it is way how to decrease dimensions of optical power splitter. Position of PhC in structure of optical power splitter can change splitting ratio.

For high-bit rate and long-haul receivers in optical telecommunication systems the avalanche photodiodes are preferred since they offer an improvement of the receiver sensitivity by several decibels. Recently critical sensing and imaging applications stimulated development of modified avalanche photodiodes structures operating in 1.55 μm spectral range. For these devices speed is not further critical. Instead, very low current densities and low multiplication noises are the main requirements. The most advanced structure of avalanche photodiodes is known as Separate Absorption, Grading, Charge and Multiplication (SAGCM). In the present work the performance of uncooled InGaAs/InAlAs/InP avalanche photodiodes operating near 1.55 μm has been studied theoretically. Device modeling based on advanced drift - diffusion model with commercial Crosslight APSYS software has been performed. Conventional SAGCM avalanche photodiodes as well as devices with a relatively thick undepleted p-type InGaAs absorption region and thin InAlAs multiplication layer have been considered. This type of avalanche photodiodes enables to increase device quantum efficiency, reduce dark current and eliminate impact ionization processes within absorbing layer. Extensive calculations allowed for detailed analysis of individual regions of the device and determination of their influence on diode characteristics.

Ionization of atomic systems by strong and short laser pulses is considered in a new gauge invariant version of the Strong Field Approximation (SFA). The standard version of SFA (SSFA), which is usually applied to the theoretical description of interaction with strong laser fields, is dependent on the choice of gauge of the vector potential describing the laser radiation. Theoretical predictions of SSFA may differ significantly depending on the choice of gauge. In particular, substantial differences have been observed in the case of two most frequently used length and velocity gauges. Gauge invariant expression for the ionization amplitude was obtained by grouping consequently all terms which are of the same order in atomic potential, treated as a perturbation compared to strength of the coupling with external laser field. Contrary to previous gauge-invariant formulations the present approach does not require different gauge-dependent partitions of the Hamiltonian. Preliminary tests of the present approach applied to ionization of Hydrogen atom show qualitative agreement with results obtained by solving numerically Time Dependent Schrödinger Equation (TDSE).

Collision-Induced hyper-Rayleigh light scattering (CIHRS) on super-molecular compounds composed of lighter noble gas atoms (He, Ne and Ar) and linear hydrogen molecules has been recently discussed within theoretical as well as numerical comparative spectral studies. The aim of the present report is to analyze updated results in this field of inter est generalized over the case of two heavier units of H2Kr and H2Xe. The roto-translational collisional profiles are obtained by means of quantum mechanical and semi-classical calculations. Tensorial symmetry adapted components of the first hyperpolarizability, Δβ – responsible for occurrence of the CIHRS processes – are applied on the grounds of previously calculated Cartesian quantities, found by means of the quantum chemistry (ab initio) methods. The spectral lines evaluated are partially treated as a benchmarking device to estimate the importance of the long-distance Δβ(R) dependence determined on the basis of the theoretical multipole-induced-multipole analytical model. Moreover, the magnitude of the CIHRS effect is discussed in regard to the experimental feasibility of CIHRS detection.

In this paper authors present a novel idea for reconstructing quantum states of polarized optical field expressed in the one-photon basis. The quantum state reconstruction is a measurement of a quasidistribution function P that allows to obtain a density operator for the analyzed state. The most commonly used approach for a quantum state reconstruction is based on the so called quantum tomography. The marginal probability distributions for the Wigner function are measured for different angles of projection and then they are put together into the two-dimensional distribution by the inverse Radon transformation. In our approach the analyzed field is combined with the reference field which is well defined, it can be for example a photon-beam containing linearly polarized photons only. The proposed thought experiment assumes that we measure the degree of linear polarization of this combined beam using a rotating polarizer. We obtain the searched distribution P by changing the parameters of the reference beam – its intensity and state of polarization. This series of measurements allows to build the system of equations The values of the function P at various points P(θ i, ϕ j) are the searched variables of this system. Accuracy of that solution depends on how many measurements are done.

In this article we provide a short theoretical background of squeezing states of light. Mainly we focus on the photon number squeezing. We are interested in detection photon number squeezed states of light by ICCD camera. It is shown how the quantum efficiency of huge multi channel detector influences a measurement of photon number statistics. The theoretical results are compared with the experimental measurement of the photon statistics of twin beams emitted by nonlinear crystal BBO pumped by intense femtosecond UV pulse. We also discuss the importance of correlation area size of beams to improving detection techniques.

On the interface between two isotropic linear media the re°ection and transmission of separate monochro- matic waves occur in a normal incidence, which are described by Fresnel's formulas. On the interface between two nonlinear media, namely one of the media may be linear in a limit, the re°ection and the transmission are complicated by a wave mixing of di®erent frequencies. A maximum generality of improved Fresnel formulas is impossible. By using the rotating-wave approximation and the parametric approximation, a model of the parametric down-conversion has been derived in the nonlinear and quantum optics. We present a classical ex- pression of the e®ect of the wave mixing on the interface and treat even the possibility of quantum input{output relations.

On the interface between two isotropic linear media the re°ection and transmission of separate monochro- matic waves occur in a normal incidence, which are described by Fresnel's formulas. On the interface between two nonlinear media, namely one of the media may be linear in a limit, the re°ection and the transmission are complicated by a wave mixing of di®erent frequencies. A maximum generality of improved Fresnel formulas is impossible. By using the rotating-wave approximation and the parametric approximation, a model of the parametric down-conversion has been derived in the nonlinear and quantum optics. We present a classical ex- pression of the e®ect of the wave mixing on the interface and treat even the possibility of quantum input{output relations.

We discuss the simulation method allowing modeling of quantum unitary dynamics for quantum nonlinear scissors systems. In particular, we consider the model of two nonlinear oscillators (Ker-like coupler) excited by an external field. We show that the time-evolution of the system is closed within a finite set of n-photo states and the Bell-like states are generated. Thus, we prove that the numerical method applied can be used as tools of quantum-mechanical simulations leading to the interesting results.

A nonlinear Kerr-coupler with nonlinear interaction between its parts is analyzed as a source of qutrit-qubit entanglement. Formation of maximal entanglement within 3⊗2 system is found and various types of entanglement decay (asymptotic and sudden entanglement death) in the amplitude damping reservoir are considered.

We present experimental characterization of periodically-poled KTP waveguide studying the process of second harmonic generation. Spatial and spectral properties of three types of the nonlinear processes (Type 0, I, and II) have been observed simultaneously utilizing the first, second, and third harmonics of the spatial nonlinear modulation. Experimental results have been interpreted using a model based on scalar finite elements method, which has been adopted in order to calculate spatial mode profiles, propagation constants, and frequencies of the interacting fields. Correlations between spatial and spectral properties of the fundamental and second- harmonic fields have been revealed. Individual nonlinear processes can be switched on and off combining spatial and spectral filtering. Also the influence of waveguide parameters to the second-harmonic spectra has been addressed.

The wavelength-division multiplex (WDM) systems represent the key technology for future optical networks. Next step for achieving the improvement of transmission system and growth of capacity is employment of high-order modulation formats. This paper provides an insight into the numerical investigation on one of the most detrimental degradation effect in multichannel systems – four-wave mixing (FWM) and its impact on transmitted signals which used novel types of high-order square and star quadrature amplitude modulation (QAM) formats, respectively. This type of nonlinear effect causes inter- and intra-channel crosstalk interference, what are the worst cases of all possible channel impairments, because all spectral properties of transmitted signal are mixed together resulting to the decreasing system performance. Our investigation is based on finding the precise solution of coupled nonlinear Schrödinger’s equations (CNLSE) for DWDM system with channel spacing according to the ITU-T standardization. For solving CNLSE, it was created numerical model through mathematical method referred as split-step Fourier method (SSFM). The investigation is oriented especially on QAM formats, different kinds of optical fibers which are typically used in today’s networks and various types of system parameters such as value of channel spacing, input power and number of channels. The obtained results are discussed and analyzed with the aim of finding the most optimal and suitable properties of DWDM transmission system.

Today's requirement for the transfer of information requires the use of broadband transmission systems. This need has successfully addressed the use of WDM systems, where the transmission of multiple channels should address the impacts of dispersion and nonlinear phenomena that occur during transmission. To describe these effects is useful to solve the nonlinear Schrödinger equation (NLSE), which is a second order partial differential equation. It’s hard to be solved by analytical methods. This paper deals with using one method of the group of finite-difference methods, the socalled method of lines to solve NLSE. The first part is focused on the propagation of the unchirped Gaussian pulse in optical fiber including group velocity dispersion and then we investigated the effect of GVD in the spread of two Gaussian pulses in the same optical fiber. The results show the interaction of these pulses. Then we have focused on the behavior of different chirped Gaussian pulses propagating in optical fiber in anomalous dispersion regime.

In this paper we consider a generalized double dispersion equation of Porubov’s type^4,5. which describes the propagation of the longitudinal strain waves in the rod. By analogy with the optical case², the higher orders of nonlinearity have been included which leads to an interesting class of traveling solitary waves for both cases: without cubic nonlinearity and with its presence. The F-expansion method described in3 has been used. As a byproduct, we obtain the results given previously by other authors^4,5. It will be shown that our analytical solutions describe very well the results obtained by numerical simulations⁶.

The article describes the basic principles and the use of X-ray microtomography which has emerged as a new promising method of measurement and non-destructive testing. X-ray microtomography (μCT) combines the principles of X-ray shadow microscopy together with the computed tomography CT. The current technical possibilities allow achieving submicron resolution by the use of experimental as well as commercial μCT facilities. Use of this method can be found particularly in materials research, precision engineering, and electronics industry. In all these areas there is a need for a non-destructive, high resolution visualization of internal microstructures, measurement of interior dimensions of 3D objects, materials testing for the presence of internal defects. Unlike the nondestructive μCT, the conventional testing methods require for the observation of internal structures mechanical cutting of the object and thus its destruction. Such damage of the object under study is often unacceptable, especially when it concerns an object of research, which should be preserved in integrity for its uniqueness or need to take further measurements and tests. Besides the materials research, there are also many other important areas of application of X-ray microtomography measuring method: electronics and precision mechanical engineering industry, mineralogy, geology, biology and archeology. In the experimental part of this article the results achieved in the microtomography laboratory of Slovak Academy of Sciences, equipped with the GE phoenix|x-ray nanotom 180 facility, will be presented.

Water Cherenkov detectors are used for studying of high energy cosmic rays. The photomultiplier tubes observe the Cherenkov light generated by fast extensive air shower of charged particles in water. Material trade-named Tyvek is frequently used as the inner lining material of these Cherenkov detectors because a high diffuse reflectivity is required in order to improve light collection uniformity. The results of Tyvek surface microstructure measurement using optical (confocal microscopy) and mechanical (profilometry) methods are presented in this paper. Tyvek surface light scattering anisotropy is commented.

The number of devices and methods for non-contact solid surface measurement and mapping is growing. Nevertheless contact devices still have value in measuring roughness, waviness and shape measurement. Modern contact devices measure without any negative influence to the surface and are even used for optical and other sensitive surfaces. Some examples are mentioned in the article below.