This PDF file contains the front matter associated with SPIE Proceedings Volume 6785, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Surface plasmon oscillations (SPO) a "new type of light" are used for high resolution sub-wavelength near field microscopy and described as the possible "substance" of all-optical chips. The statistical properties of SPO-s are analyzed, based on SPO images taken by this type of microscopes and time dependent correlation analysis.

The ytterbium-doped crystals emitting around 1 μm under laser-diode pumping between 900-980 nm have received an increasing interest in recent years as solid-state laser materials for high power or ultra-fast lasers. In this paper, our main objective is to contribute to Yb³⁺-doped fluorides mainly on CaF₂ cubic host which are characterized by a high value of the thermal conductivity (9.5 W m^-1 K^-1) as high as YAG. Yb³⁺-doped CaF₂, mono-doped and concentration gradient fibres were grown by both, the laser heated pedestal growth (LHPG) method and by the Czochralski method. Concerning Yb³⁺ excited state dynamics, the concentration dependence of the ²F_5/2 decay time shows a competition between self-trapping and self-quenching processes. Main parameters useful for a theoretical approach of laser potentiality will be given and laser emission under InGaAs laser-diode pumping will be shown.

The output performances of thin disk lasers with Nd-based gain media are investigated under multi-pass pumping with diode lasers at 808 nm into the ⁴F_5/2 level and directly into the upper ⁴F_3/2 emitting level. Continuous-wave operation with powers in excess of 10 W at 1.06 μm, and in the watt-region at 0.94 μm in Nd:YAG and at 0.91 μm in Nd:YVO₄ and Nd:GdVO₄ is obtained. Intracavity frequency doubling of the 0.91-μm emitting Nd:vanadates lasers generate 'deep-blue' light in excess of 1 W under pumping into the ⁴F_5/2 level; results on blue-emitting thin disk lasers that are pumped at ~0.88 μm into the ⁴F_3/2 emitting level are presented for the first time. Simultaneous dual-wavelength emission on the ⁴F_3/2→ ⁴I_9/2 quasi-three-level transition and the 4F_3/2→ ⁴I_11/2 four-level transition is demonstrated from all these media.

In this paper we report some experimental and theoretical results concerning the evaluation of some spectroscopic parameters which characterize the Er³⁺ and Yb³⁺ doped LiNbO₃ optical waveguide amplifiers. The transmission spectra were used to determine the homogeneous absorption and emission cross sections (utilizing the density matrix formalism and the McCumber's theory and taking into account the Stark splitting of the levels), the oscillator strength of the absorption transition, the spontaneous emission probabilities, radiative lifetime and the excitation energy in the near IR region of the optical spectrum: around 1530 nm and 980 nm, respectively. The obtained results are in good agreement with other ones published in the literature in the last few years and can be used for the theoretical modelling of the guided lasers and amplifiers, design of guided optoelectronic devices etc.

Diode edge-pumped microchip Yb:YAG/YAG laser with a special design of the optical resonator was combined with LBO crystal in the nonlinear mirror configuration to obtain high power mode locking operation. 84.8 MHz pulse repetition rate of mode-locking oscillation was obtained with an average power of 30-W in quasi-CW operation with 10% duty factor.

Generation of a radially polarized laser beam was demonstrated by using birefringence of a c-cut Nd:YVO₄ crystal. The c-axis of the Nd:YVO₄ laser crystal was parallel to the optical axis of the laser cavity. High power, single emitter semiconductor lasers were used for the pumping of the laser crystal in the side-pumping configuration. By adjusting the cavity length, only the radially polarized light corresponding to extraordinary light in the Nd:YVO₄ crystal was selectively enforced to oscillate because the refractive index for the ordinary light differs from that for the extraordinary light. Good stability of the output power against the mechanical noise was achieved owing to the outstanding simplicity of the cavity configuration.

A compact single-frequency nanosecond green laser oscillator-amplifier system was developed. The single longitudinal mode oscillator consists in a cavity-coupled acousto-optically Q-switched Nd:YAG microlaser emitting pulses of 50 μJ energy, 10 nanosecond duration at 1064 nm wavelength. The oscillator pulses were amplified at 1-10 Hz repetition rate in a two-pass Nd:YAG amplifier up to 28 mJ energy. Infrared amplified radiation was frequency doubled (532 nm) in a KTP crystal with as much as 50% conversion efficiency. The pulsed green laser, with more than 1.5 m coherence length, was used as light source for the holography unit in the sensor of a multi-task device for nondestructive diagnosis in art conservation procedures.

We analyze, using the fluorescence spectroscopy of Eu³⁺, two partially disordered crystals from the langasite family: langasite and langatate. There are two main differences between these crystals: (a) the randomly occupied positions (Ga³⁺ - Si⁴⁺ in tetrahedral positions for langasite and Ga ³⁺ - Ta ⁵⁺ in octahedral positions for langatate) and (b) the charge difference between the ions in these positions (1e for langasite and 2e for langatate). For LGS:Eu, the presence of multiple fluorescent centers could not be evidenced, while for LGT:Eu the splitting of the fluorescence lines clearly indicates the presence of multiple fluorescent centers.

Optical and Mossbauer spectroscopy were used to put into evidence the morphological changes induced by the thermal treatments in the YAG:Eu nanocrystals synthesized by a sol-gel method. Both methods exhibit a drastic change of the monitored parameters (ratio of the areas of the electric and the magnetic dipole transitions - for optical spectroscopy and Mossbauer normalized area - for Mossbauer spectroscopy) at the phase transition amorphous-crystalline, followed by a slow evolution of these parameters with the increase of the annealing temperature. This slow evolution is due to the increase in size of the nanocrystals.

We present a new geometry for edge-pumping of a solid-state microchip laser. This design, which consists of a thin-disk gain crystal surrounded by a diffusion bonded undoped material that guides the pump light, allows a good thermal heat management by reducing the thickness of the gain media, whereas the pump optics is kept simple. The upper surface of the gain media has concave-spherical shape that allows easy confinement of the pumping power to laser gain media thinner than 100 μm. Simulations show that more than 0.95 of the pump radiation with uniformity coefficient in excess of 0.96 can be absorbed in an Yb:YAG/YAG composite device that has a 50-μm thick, 10-at.% Yb:YAG of 3 mm diameter.

The spectroscopic investigation of the highly transparent rare earth (Pr³⁺, Nd³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺) doped Sc₂O₃ ceramics produced by the solid-state synthesis technique indicate that these materials could substitute the single crystals in construction of solid-state lasers. These studies indicate also that the rare earth doped transparent ceramics could extend considerably the variety and performances (new active systems, wavelength ranges or emission schemes) of these lasers.

The main component of the free electron laser is the undulator. Besides the numerical computation approach of the magnetic field generated by the undulator current, the other possibility is the analogic simulation. Such an approach is more intuitive and also enables a validation of the numerical simulation. The undulator consists of a Huygens wires stack. In each wire of the stack the current circulates alternatively from a wire to another. The magnetic field mathematical model for a wire uses operations like multiplications, divisions, radicals, trigonometric functions and integrations. These operations were simulated by using an harmonic oscilator (using MC1458 amplifiers), analog multipliers (AD633) and integrators (using MC1458 amplifiers).

Thin films of boron nitride were grown by femtosecond, pulsed laser deposition. The films were analyzed by transmission electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. All the results indicated the presence of wurtzite phase in the thin film in contrast to usual phases such as cubic or hexagonal ones. Moreover, the electron diffraction pattern showed that the size of the wurtzite boron nitride crystallite was larger than 4 μm although boron nitride films reported so far consisted of small crystallites in the nanometer region.

The influence of the irradiation conditions on plume expansion induced by femtosecond laser ablation of gold and copper is investigated experimentally involving measurements of the ablated mass, plasma diagnostics, and analysis of the nanoparticle size distribution. The targets were irradiated under vacuum with a spot of uniform energy distribution. Only a few laser pulses were applied to each irradiation site to make sure that the plume expansion dynamics were not altered by the depth of the laser-produced crater. Under these conditions, two main components were observed by fast imaging. They were identified by optical emission spectroscopy: the fast component is composed of atoms and ions whereas the slow one mainly contains nanoparticles. Experiments show that the velocities of plasma species depend weakly on laser fluence. Deposition of nanoparticles on a substrate and analyses by atomic force microscopy show that the size distribution of nanoparticles does not exhibit a maximum and the particle abundance monotonously decreases with size. Furthermore, the results indicate that two populations of nanoparticles exist within the plume: small clusters that are more abundant in the fast frontal plume component, and larger particles that are located mostly at the back. It is shown that the ablation efficiency is strongly related to the presence of nanoparticles in the plume.

An optical sensor based on MMI structures has been studied. We have used the optical parameters of a new hybrid material deposited by sol-gel method leading to waveguide structures after UV-photoinscription, and of ZnO, sensitive material characterised in previous studies. The variation of optical properties such as the refractive index of the covering sensitive material leads to a modification of waveguiding conditions in the MMI. A gas sensor can be developed by measuring the variation of light intensity at the output of the MMI structure under gas exposure. Simulations have been performed in order to optimise the output light intensity variations to increase sensitivity. We have shown that these structures are more sensitive than Mach-Zehnder interferometers, and that the relation between dimensions and sensitivity of the MMI is not trivial. Computations have to be performed to optimise the structure for given parameters.

The structure and optical properties of AlN thin films synthesized at 800°C by Pulsed Laser Deposition were studied in terms of ambient nitrogen pressure (10^-4-10 Pa) and post-deposition cooling rate (5-25°C/min). X-ray diffraction patterns showed the films were polycrystalline with predominantly cubic phase and small-sized crystallites. The refractive index and oscillator energies values were also characteristic of the polycrystalline AlN with cubic structure.

We investigate triplet bound-states with a new symmetry, called "cis", using the cubic-quintic CGL equation. We show that the leading term of the functional J[ψ], which governs the evolution of the momentum of the solution to the CGL equation, vanishes for the cis symmetry. Numerical investigation show that stable cis triplet bound states are solutions of the CGL equation. Quasi-stable cis states are also found, and also a stable quasi-stationary asymmetrical triple state. Then we show that it is possible to experimentally distinguish between the trans and cis triplet states, using either the optical spectrum or the collinear autocorrelation trace.

A quantum dot - immunoglobulin conjugate specific for pig IgG, was obtained by carbodiimide chemistry. We used a Western blot technique for detecting specific antibodies against Actinobacillus pleuropneumoniae (A. pp), which cause porcine pleuropneumonia. The antigen used in this technique was Apx haemolysin which is an important virulence factor of A. pp and it induces protective immunity in vaccined pigs. The detection on Western blot membrane was possible at 1/50 dilution of quantum dot conjugate at a dilution of pig serum till 1/6400. The results for pig serum demonstrated a higher sensitivity of QD-based Western blot technique for the presence of antibodies specific for Apx haemolysin in comparison with similar classical techniques (with coloured substrate for enzyme present in secondary antibody conjugate).

We report the functionalization of Si/SiO₂ Quantum Dots (QDs) synthesised by laser ablation. Our interest has been to increase the affinity of the QDs surface for organic substances, in order to obtain QD-immunoglobulin conjugates, particularly for biolabeling. We have studied the UV-induced graft polymerization of the freestanding nanoparticles. High resolution transmission electron microscopy and laser granulometry, were used to obtain information on particle and cluster size distribution, degree of agglomeration, etc. The polymer-dot complexes appeared as relatively well-defined clusters, QDs being surrounded by a polymer layer with thickness 3-10 nm. The size of the primary clusters was in the range 60-500 nm. The polymerization and filtration process (0.1 μm pores) involved a diminution of the clusters size in the range of 18-65 nm, and moreover, by a subsequent dialyses process the cluster size decreased to 5-15 nm.

This work proposes to analyze the behavior of austenitic manganese - Hadfield steel during laser beam welding in continuous regime. In order to limit the number of experiments, a 2⁴ type factorial experiment was used, with 16 assays, after a frequently used program matrix for these situations. Fusion lines at different service regimes, as well as head to head welds were performed. Microhardness measurements and microstructure modifications that appear as an effect of laser irradiation are also analyzed.

The synthesis of strongly luminescing semiconductor nanocrystals reported is based on a wet-chemical approach. The use of aqueous solutions and the avoiding of dangerous and unstable precursors make this synthetic approach to be easily up-scaleable. The reaction yields are approaching gram amounts of the dried product and are limited solely by the laboratory facilities and thus may be further increased by using industrial equipments. The nanocrystals obtained by this route are strongly luminescing and suitable for various assembling procedures allowing the creation of core-shell spherical and thin-film composites, that are promising for photonic and optoelectronic applications. New assembly procedures allowing template-based formations of different types of metal-dielectric and porous metal nanostructures are presented.

New composite and nanocomposite materials consisting from amorphous chalcogenide (As₂S₃, As₂Se₃) and polymers such as polyvinylalcool (PVA) and polyvinylpyrrolidone (PVP) were prepared by inexpensive and easy coating technique from chemical solution and were investigated. Composite retains many properties of the initial components from which they are prepared. Morphology and optical properties of deposited materials in the form of films are presented. The decreasing of the As₂S₃ component in the composite leads to the shift of the absorption edge to higher energies and spheroid dimensions are decreased. For the samples As₂S₃:Pr³⁺/PVA an increasing of transparency in the visible region with respect to pure As₂S₃ was observed. As a result of ultraviolet light irradiation of the composites change of optical properties is observed. For example the refractive index may be change in value 0,1. This allows utilizing these structures for holographic recording of diffraction gratings. The investigated new composites are perspective for different photonic devices as well as for recording media with high resolution.

The objective of this study is to develop a procedure for controlling the deposition of colloidal crystal coatings from nanoparticle suspensions. We experimentally deposited polystyrene nanospheres on glass plates by dragging a small volume of liquid over the substrates. The mechanism governing the deposition is convective assembly. It has been observed that the number of deposited nanosphere layers can be influenced by the deposition speed and the nanosphere volume fraction, as predicted by theory. Crystal coatings of a few square centimeters were deposited in minutes from suspensions of 5 - 20 μL. Our computer simulations of the phenomena generated structures similar to those from experimental films, proving the validity of the model elaborated for the assembly process.

We measure electronic and thermal nonlinear refractive indices of periodically nano-patterned and un-patterned siliconon- insulator (SOI) in comparison with that of bulk silicon, using a fast reflection Z-scan setup with a high-repetition-rate fs laser (at 800 nm wavelength), and a new procedure for discrimination between electronic and thermal nonlinearities. The electronic nonlinear response of nano-structured SOI is strongly enhanced in comparison with those of un-patterned SOI and of bulk Si. These results could be important in silicon photonics for optical devices with nonlinearity controlled by periodic nano-structuring.

The exact solution for the system of three atoms in interaction with microcavity mode of electromagnetic field is analyzed. The problems of quantum nutation of atomic inversion and entanglement between the cavity field and collective atomic states are described. The application of this effect in micromasers is discussed. The condition for lasing and trapping effects is found. The quantum properties of cavity field are studied.

We prove that a beam of non-quantum particles going through a double-slit may concentrate in some locations while avoiding others. Their detection shows maxima and minima which do not appear from the interference of some waves, but are a consequence of the interaction between particles and the screen. The model is an application of cellular automata. This behaviour is the result of two assumptions: we allow small diffusions on both sides of the main stream of particles; particles are reflected by the screen as if the obstacle would be a particle supplier. We attempt an explanation of these results.

A new reversible effect of three-level atom in interaction with quantum bimodal cavity field is proposed. The problem consists in the possibility of realization of initial separate state of atom and electromagnetic field after flying time through the cavity field. The discrete values for the flying time interval, which corresponds to the reversibility of the quantum states, were found. The quantum properties of bimodal field, which satisfy the optical trapping conditions for the atom flying through the cavity, were studied. The recursion relation for the amplitude of the electromagnetic field in decompositions on the Fock states was obtained.

We have developed a scanning confocal microscopy (SCM) system which can be used to investigate micro-structural properties of samples with micro-geometry. We present advantages of this imaging technique for visualization and characterization of some periodic and non-periodic (porous silicon with an alveolar columnar structure (1.5 - 3 μm pores diameters)) samples. Using the confocal microscopy, we can obtain an enhancement of image resolution and contrast, in comparison with conventional optical microscopy. Therefore, it has particular advantages for the study of porous silicon. Confocal imaging method permit the "optical sectioning" of samples and lead to a sub-micron resolution both in lateral plane and axial plane.

Photoinduced molecular reorientation in dye-doped liquid crystal cells has been studied for a set of azodyes with a "pump-probe" optical device. The rotating angle of the nematic director as a function of irradiation time has been calculated. The lateral chemical groups of the azo-dye molecules have not an important influence on the orientation effect; this aspect supports the idea that the trans-cis photoisomerization of the dye molecules is the predominant mechanism responsible for the molecular reorientation in azo-dye-doped liquid crystal systems.

We report recent results obtained with volume holographic gratings recorded in a new photopolymerisable glass modified with high refractive index species at molecular level. Various not previously observed performances have been achieved for diffraction efficiency and angular selectivity. In particular, new overmodulation effects have been observed for the first time experimentally in an amorphous material.

We developed a visualization method to display nano-particles and their dynamic 2D growth and coalescence on surfaces, due to mechanisms such as adsorption, diffusion and coalescence. The method relies on 2D spatial Fourier frequency transforms (FT) of 2D image density functions representing the details of the x-y-z nanostructure. These images are convoluted using FT of spatio-temporal integrodifferential equations involving models of the physical driving forces in the spatial frequency domain. Surface growth and restructuring effects taking place during photo-deposition processes were investigated. In particular, the dynamic changes of photo-deposited nanoparticles morphology during sub-monolayer growth were simulated. The comparison of simulation and sampled Scanning Electron Microscopy (SEM) micrographs of photo deposited thin films during monolayer formation were in good agreement.

The dynamics of solitary pulses in an inhomogeneous nonlinear-optical waveguide, and in Bose-Einstein con-densates controlled by means of the Feshback-resonance techniques with a time-dependent magnetic field, which usually includes dispersion and nonlinearity management as typical scenarios, obeys a variable-coefficient non-linear Schrödinger (NLS)/Gross-Pitaevskii (GP) equation. In this paper, we survey approaches that make it possible to identify special cases of such equations that admit families of exact solutions obtained by means of the Hirota bilinear method. In particular, pulse compression and chirp effects are studied by means of this technique. The method is shown to be effective in modeling the evolution and interaction of solitary pulses.

Using Maxwell-Bloch equations, we analyze the response of a two-component medium of two-level atoms driven by a two-cycle optical pulse beyond the traditional approach of slowly varying amplitudes and phases. We show that the notions of carrier, envelope, phase and group velocities can be generalized to this situation, and that for optical pulses of a given duration, the optical field can evolve into temporal few-cycle solitons.

In this work we investigate the dynamics of a spatial soliton pulse under the presence of a linear Periodic Wave (PW), which dynamically induces a photonic lattice. We consider that propagation phenomena are governed by the well-known non-linear Schrodinger equation (NLSE), while Kerr-type non-linearity is in effect. Interaction phenomena are analyzed by forming a non-linear coupled differential equation system of the evolution of the soliton-beam parameters. Direct numerical simulations of the NLS equation are shown to be in good agreement with the solution of the dynamical system, for a wide range of the parameters.

We consider the three-dimensional (3D) Gross-Pitaevskii/nonlinear Schrodinger equation with a quasi-2D square-lattice potential, which corresponds to the optical lattice trapping a self-attractive Bose-Einstein condensate (BEC), or to a photonic-crystal fiber, in terms of nonlinear optics. Stable 3D solitons, with embedded vorticity S = 1 and 2, are found by means of the variational approximation and in a numerical form. They are built, basically, as sets of four fundamental solitons forming a rhombus, with phase shifts πS/2 between adjacent sites, and an empty site in the middle. The results provide for the first examples of stable 3D vortex solitons ("spinning light bullets", in terms of optics) with S > 1, and the first ever examples of vortex solitons (with any S ≠ 0) supported by a lattice in the 3D space. Typical scenarios of instability development (collapse or decay) of unstable localized vortices are identified too.

We give a brief overview of recent results in the area of two- and three-dimensional doughnut-shaped localized structures with the inner phase fields in the form of rotating spirals, in the paradigmatic model based on the complex Ginzburg-Landau equation with competing cubic-quintic nonlinearities. It is shown that very robust two-dimensional and three-dimensional dissipative spiral solitons with (at least) the values of the topological charge S = 0, 1, and 2 can be easily generated from a large variety of inputs with embedded vorticity.

An adaptive fiber-optical interferometer, which is based on dynamic reflection hologram recorded in the photorefractive crystal of cubic symmetry without applying any electrical field, is developed. Adaptive properties of dynamic hologram enable the solution of an interferometer's working point uncontrollable drift problem caused by external factors. Theoretical analysis has allowed us to find the optimal set of parameters for both interacting waves and crystal to reach the maximal sensitivity of the measuring system. Use of semiconductor crystal CdTe with fast recording time of a dynamic hologram makes it possible to achieve high cutoff frequencies at reasonably low light intensities. As a result the measuring system is characterized by low energy consumption and ability of stable operation of long duration in industrial environment.

A new architecture with two phases-only diffractive elements and one decryption mask for optical control access system is presented. Only three different persons which keep this element have the permission to access together. The Iterative Fourier Transform Algorithm (IFTA) is analyzed for phase-only diffractive optical elements (PODE) design with different constraints in the input and output plane and the optimal variant is chosen for better image quality in the output plane (big value for diffraction efficiency and small value for merit function and signal to noise ratio). For higher security we propose different incident waves. That are compared with the case when the first phase-only diffractive element and decryption masks are designed together in an extended iteration and the output images of them (first desired image) is taken over the second phase-only diffractive element. In order to increase security level, this finally PODE are designed to increase some parts from the first desired image. Only with this condition the key image on the detector is formed.

The existence and robustness of dark vortices in bi-dispersive and/or normally dispersive self-defocusing nonlinear media is demonstrated. The underlying equation is the bi-dispersive three-dimensional nonlinear Schrödinger equation. These solutions can be considered as extensions of two-dimensional dark vortex solitons which, along the third dimension, remain localized due to the interplay between diffraction and nonlinearity. Such vortex solitons can be observed in optical media with normal dispersion, normal diffraction, and defocusing nonlinearity.

We present the investigation of second harmonic generation in congruent undoped lithium niobate crystal in presence of strong photorefractive and photovoltaic effect. We show that phase matching condition can be efficiently varied employing both the temperature and the electric field tuning. We also perform experiments on second harmonic generation with focused light, showing that the photorefractive effect is responsible for a strong distortion of the beam as well as a local modification of the phase matching condition. Finally, we demonstrate that an external bias can be used in order to switch from optical damage and distortion to self-confinement and guidance, reaching higher conversion efficiency through confinement and good overlap between interacting waves.

We report in this paper a theoretical analysis of some parameters which characterize the Er³⁺-doped Ti:LiNbO₃ straight waveguide amplifiers. The derivation and the evaluation of the spectral optical gain, the spectral noise figure, the signalto- noise ratio and the amplified spontaneous emission photon number are performed under the small gain approximation taking into account the overlap between the pump, signal and dopant distribution profiles. In our simulations the Er³⁺- profile is considered erfc, Gaussian or constant in depth and Gaussian in width, with a surface concentration of about 7•10²⁵m^-3 and a diffusion depth of 20 μm.

Polymeric multilayer Bragg structures are combined with diffractive gratings to produce artificial visual color effects. A particular effect is expected due to the angular reflection dependence of the multilayer Bragg structure and the dispersion caused by the grating. The combined effects can also be used to design particular filter functions and various resonant structures. The multilayer Bragg structure is fabricated by spin-coating of two different low-cost polymer materials in solution on a cleaned glass substrate. These polymers have a refractive index difference of about 0.15 and permit multilayer coatings without interlayer problems. Master gratings of different periods are realized by laser beam interference and replicated gratings are superimposed on the multilayer structure by soft embossing in a UV curing glue. The fabrication process requires only polymer materials. The obtained devices are stable and robust. Angular dependent reflection spectrums for the visible are measured. These results show that it is possible to obtain unexpected reflection effects. A rich variety of color spectra can be generated, which is not possible with a single grating. This can be explained by the coupling of transmission of grating orders and the Bragg reflection band. A simple model permits to explain some of the spectral vs angular dependence of reflected light.

We report on the unusually high optical transmitivity of silver coated two-dimensional colloidal crystals. Our sample consists of a 50 nm silver film deposited on top of a regular two-dimensional array of polystyrene spheres of 400 nm diameter. Two-dimensional colloidal crystals were prepared according to the drop-coating technique, and subsequently covered in a silver film by thermal evaporation. Morphology of the crystal was checked by means of scanning electron microscopy. We measured transmission through the composite metallo-dielectric films at normal and also oblique incidence. Additional reflectance spectra and surface enhanced Raman scattering are used to understand the optical/plasmonic properties of the prepared nanostructure. Dependence of the spectral features on incident angle suggests highly localized optical/plasmonic modes are involved in the mechanism of transmission.

The visible luminescence from Pr³⁺, Dy³⁺, Nd³⁺, Sm³⁺ and codoped with Ho³⁺ and Dy³⁺ ions embedded in Ga_0.017Ge_0.25As_0.083S_0.65 glass hosts at room temperature and at T=10 K is reported, when pumping with an Ar⁺-ion laser at λ=488 nm. Fluorescence emissions at 1.3 μm was observed for Dy³⁺ and both at 1.3 and at 1.5 μm for Pr³⁺ doped glasses with wavelength pumping at 950 nm. Energy transfer from Ho³⁺:⁵F₃ level to Dy³⁺:⁴F_9/2 level increase the visible emission efficiency at 650 nm in the codoped glasses. The investigated Ga_0.017Ge_0.25As_0.083S_0.65 glasses doped with Pr³⁺ are promising amplifier materials for 1.3 and 1.5 μm fiber optic telecommunication windows.

In this paper we are going to present some results regarding the optical trapping and manipulation of dielectric microparticles immersed in fluids. The experiments will be done in Mie regime, i.e diameter of the particles is larger than the laser wavelength. We will report optical trapping of multiple particles and their manipulation by means of optical tweezers setup. To catch microobjects we will use a Gaussian laser beam and to manipulate them we are going to calculate diffractive optical elements (DOEs) by iterative algorithm and spherical wave method.

Photonic crystal optical waveguides have the major advantage of maintaining light, confined inside them, even if the guide has sharp bends or splits into secondary optical channels. However, inside a certain network of waveguides with ramified branches, unwanted reflections still exists and in consequence modalities for reducing the energy sent back to the source and maximizing the one transmitted, have to be found. The purpose of this paper is to study the performances of a combined procedure which uses analytical formula and numerical simulations and whose final aim is focused on improving transmission and minimizing reflections.

Photorefractive (PR) spatial soliton propagation hints that all optical routing can be achieved through soliton interactions. This requires, however, fast build up and sensitivity to telecommunication wavelengths. We have investigated the build up of infrared (1,06m) photorefractive solitons in iron doped indium phosphide (InP:Fe) and shown that PR self focusing occurs at input powers of hundreds of W and intensities in the range of W/cm², showing a build up time down to the microsecond.

We present an envelope formalism describing nonlinear phenomena in photonic crystals by casting the Maxwell equations as a linear Hermitian eigenvalue problem in close analogy with the Schroedinger equation of quantum mechanics. From this formulation, applied to one dimensional photonic crystal, comes a variety of useful properties, including the density of modes and second harmonic generation. The mutual control of radiation field and matter defined by the control of photon modes by nonlinear photonic crystals -mode shapes, dispersion relations, optical solitons- is a key technology for future photonic devices.

Photostructural transformations in amorphous films of chalcogenide glasses (ChG) under light irradiation present scientific and practical interests. From scientific point of view, because the composition of ChG determine the kind of structural units and the mean coordination number, in the present work the amorphous films of the chalcogenide systems As_100-xSe_x (x=40÷98) and As₄₀Se₆₀:Sn_y (y=0÷5.0 at.% Sn) were studied. The changes of the refractive index under light irradiation and heat treatment are calculated from the transmission spectra. The more sensitive to light irradiation are the amorphous films of As₆₀Se₄₀ and As₅₀Se₅₀, which exhibit big modifications of the refractive index ((Δn/n)=0.394).

The thermal third order nonlinearity of a neutral density glass is measured using the Z-Scan method. The measurements are performed using two different laser configurations: a continuous wave laser at 532 nm and a femtosecond laser at 1060 nm. The measurements are used to determine the nonlinear refractive index, n₂ and the thermo-optical coefficien dn/dt of the samples. The measurements in the two different laser configurations are in good agreement with the existing theory models.

Nanocomposite materials have become very promising in the field of optical sensing. A variety of inorganic and hybrid (polymer/inorganic) material structures are prepared and evaluated as potential sensors for physicochemical monitoring applications (e.g. reducing/oxidising gases, NH₃, alcohols hydrocarbons and other). Materials response is based on their optical properties alteration such as scattering effects, refractive index changes or absorbance shifts incurred upon ambient physicochemical parameters modification. First results of response, together with surface analysis and stoichiometric and morphological characteristics of the developed materials are presented.

The reactive oxygen species (ROS) produced inside cells by UV-B radiation may induce apoptosis, a process that realizes the programmed death of cells. In the present paper the UV induced damage was studied in a human T-Lymphocyte cell line (the Jurkat line) by mean of IR laser photoacoustic spectroscopy (PAS) and by Fourier Transform Infrared Spectroscopy (FTIR) combined with biological assays based on flow cytometry. The apoptosis was induced in vitro in the Jurkat samples by exposition to UV-B radiation with a dose of 310 mJ/cm². PAS measurements were performed through a 10W c.w. CO₂ laser based optical system realised at ENEA Molecular Spectroscopy Laboratory in Frascati (Italy).

Results are presented in using low coherence interferometry in quantifying the reflectivity and imaging of different objects, such as tissue, paintings and fruits. All images have been obtained using en-face flying spot technology. This allows simultaneous generation of optical coherence tomography and confocal scanning images.

The development of better techniques for land vegetation cover and forest ecosystems monitoring is a major requirement for local, regional and global policy and global change science. The influence of climatic variability and anthropogenic activities on the condition of the vegetation (agricultural fields, forests, sparse) is growing up continuously. In order to characterize current and future state of vegetation and localize zones of changes must be defined the proper criteria. Vegetation land cover monitoring by satellite remote sensing data is one of the most important application of satellite imagery. Vegetation reflectance has variations with sun zenith angle, view zenith angle, and terrain slope angle. To better providing of this these effects corrections in the visible and near-infrared region of electromagnetic spectrum, was used a three parameters model and was developed a simple physical model of vegetation reflectance, by assuming a homogeneous and closed vegetation canopy with randomly oriented leaves. Multiple scattering theory was used to extend the model to function for both near-infrared and visible light. This paper aims to improve the model to be used to correct satellite imagery for bidirectional and topographic effects. Thresholding based on biophysical variables derived from time trajectories of satellite data was applied for classifying using Landsat TM and ETM, SAR ERS-1 imagery for Cernica forested area in the Eastern part of Bucharest town, Romania. Classification accuracies are function of the class, comparison method and season of the year.

In biological suspensions light scattering is done mainly by the contribution of the suspended cells. A main challenge in describing light diffusion is to produce an analytical expression that accurately expresses the multiple light scattering anisotropy. The Henyey-Greenstein phase function embedded in the RWMCS code was used to describe single scattering on Red Blood Cells in suspension. The results of the simulation, containing multiple light scattering, are used to verify the predictions of two new effective phase function recently published. The results show a good agreement in the small RBC concentration range.

Solar radiation is the primary source of energy that drives earth system processes, such as weather patterns and rates of primary production by green plants. Accurate solar irradiance data are necessary for the radiative forcing of the climate system assessment as well as for efficient planning and operation of solar energy systems. Topography is a major factor that determines the amount of solar radiation reaching any particular location on the Earth's surface. Its variability in elevation, surface orientation (slope and aspect), and shadows is subject to quantitative modeling, based on radiative transfer models (RTM) using atmospheric parameter information retrieved from the MODIS satellites. This paper focuses on the description of a solar radiation model to describe spatial and temporal patterns of daily radiation based on topography and daily temperature regimes with a specific analysis for Dobruja area, Romania.

Laser diodes are lighting devices in which the light is generated by stimulated emission rather than spontaneous emission, with high generation efficiency. A device using 20 red laser diodes is presented. Emission wavelengths are in the 650-670 nm range. Emission power for each laser diode is about 4 mW. This device is used to irradiate the tomato seeds with three different irradiating doses. There were three Petri vessels for each dose having 25 seeds each of them. Results show that the germination rate increases for irradiated seeds. The red light has a positive effect for vegetable cultivated in protected area.

Artificial lighting for plants cultivation is an important factor that can determine the nutritional quality of vegetables. The improvement of quality is determined by the emission spectrum of LED, suitable for vegetables. This spectrum values must be inside the solar ones. So, by using red high-power LEDs we can supplement the conventional lighting (ex. HPS) and we can enrich the red light from the emission light. We have used a special device that has 200 high-power red LEDs, having emission wavelength in 640-670 nm range, which is presented below. Using red LEDs on tomato seeds, we can observe that the germination rate significantly increased.

A modified version of the Laser Speckle Contrast Analysis technique was developed. It is different of the typical LASCA technique as the laser beam is not reflected by the object but transmitted through a cuvette containing a diluted suspension. A digital image with speckles is taken and the time contrast not the space contrast is calculated, which is the second main difference from the typical LASCA technique. The contrast is converted into colors and a contrast image, hence a velocity map is obtained. The results of analyzing different biological suspensions with this technique are presented and the possibility of using it for micrometric particle motion and as a fast diagnosis method is discussed.

To solve some microsurgical procedures in the anterior and posterior chambers using the photo disruptive effect, a special Nd:YAG nanosecond laser device is presented. The Nd:YAG laser is q-switched (Cr⁴⁺:YAG). The laser beam is expanded. After expansion, the laser beam is passed through a circular variable filter which is rotated by a processor, allowing energy to be set at any value in the range of 0.5-10 mJ. Two infrared LED-phototransistor pairs are used to position the filter. The laser beam is focused by the objective at 150 microns behind the object plane to avoid the damage of the Intraocular Lens.

The paper presents the polygon scanners used for industrial, dimensional measurements. The characteristic parameters and functions of the measuring system are ascertained: the scanning function and velocity, the two pairs of characteristic angles, the duty cycle and the two-parameters functioning characteristic. The possibilities of obtaining a one-parameter functioning characteristic are explored. A rigouros mathematical analysis of these subjects is performed, including the discussion of their diagrams, obtained not numerically, but analythic. An experimental validation of these results has been presented in a previous study. The results obtained for the optical scanner are quit general, and they are also valid for other applications of the laser scanners, besides the particular one considered in the paper. In order to complete the designing calculus of the system, the migration functions that characterize this type of scanning head, the polygon, are defined, ascertained and used, the designing steps being thus fulfilled.

The concept of refractive index has to be revisited for micro or nano structured materials. The refractive index is generally linked to the group phase velocity of the light wave traveling through a media. With such a definition it must be associated to the effective index in waveguides or in photonic crystals. This last point leads to the concept of metamaterials. The fundamental problem of the optical properties of nanostructured materials is tackled. With the progresses of nanotechnologies it becomes now possible to control the nanostructure of materials. Refractive index engineering, artificial anisotropy and antireflection structures are now possible. This paves the way to new applications concerning photonic crystals, integrated optics, micro sensors, solar cells... Some examples of applications are given.

The thin-film technology allows the fabrication of optical filters which behaviour is not uniform along the surface of the device. Such intentional non uniformity permits the selection of different wavelengths of the spectrum with a single small-dimension optical component. Each wavelength is transmitted at a given position over the component surface and this effect is obtained by depositing a graded coating on a glass substrate. This narrow-band transmission filter is based on the combination of metal and dielectric thin films, in fact this choice allows a wide operating wavelength range with a low number of layers. The optical filter coupled to an array detector gives a spectral sensor that is useful for the fabrication of small-dimension and low-weight spectrometers.

The paper presents a comparative study, by off-line measurements of the irradiation induced optical attenuation in several large diameter (600 μm) optical fibers subjected to gamma-rays and neutron irradiation. The optical fiber samples fall into two categories: optical fibers with an enhanced UV transmission (high OH content core) and solarization resistant optical fibers. The irradiation conditions were as follows: a) gamma irradiation at a ⁶⁰Co source, with a dose rate of 0.33 kGy/h +/- 5%, up to the maximum total irradiation dose of 313 kGy; b) neutron irradiation (mean energy 5.2 MeV) using a deuteron beam (13 MeV) and a thick beryllium target, for a total fluence of 6x10¹² n.cm^-2. Electron paramagnetic resonance measurements have been carried out to further investigate the radiation sensitivity of the considered fibers and to identify irradiation induced paramagnetic point defects.

In the frame of the European Union funded Comenius project "Hands-on Science", a network of very active high schools was created, aiming to attract students towards science study by offering them the possibility to learn and to express themselves through experiments. On the other side, our Institute coordinates the project "Science Education and Training in a Knowledge-Based Society - SET 2010", project supported by the Romanian Ministry of Education and Research, which targets the same audience by different means. The paper addresses some of the results of these two projects as they are linked with photonics teaching in high schools through extra curricular activities such as science clubs, science fairs, and national contests for high school students. The project results were introduced to the public at various conferences: ETOP Conference (France), NATO Advanced Workshop (Hungary), Hands-on Science Conference (Greece), Euroscience Forum (Germany), Communicating European Research (Belgium).

This paper deals with optical characterization of photo-polymer gratings for parameter control. The gratings were obtained using the photoinduced single step inscription of refractive optical elements technique. The optical characterization was done by measuring the specular and diffracted orders of a laser beam incident on the grating. This technique is specifically known as scatterometry. The laser was a He-Ne with 633 nm wavelength. The measured diffraction efficiencies contain information about the parameters to be determined of the grating, such as pitch, linewidth and shape of the ridges.

The paper presents a comparative mathematical study of the possible solutions of the double-prisms neutral density filters. After a brief overview of the optical devices used for the attenuation of light (especially in spectrophotometers and colorimeters), the three different arrangements, not only of the double-wedges, but, more generally, of the double-prisms, are considered; two of the solutions, in the double-wedges form, being but suggested in the state-of-the-art. An extension of the existing theory is thus achieved. The characteristic parameters of each of the possible solutions of this optical attenuator are defined, obtained and compared, in order to select the optimal device. From the study, the best solution of the double-prisms neutral density filters, both from the mechanical and from the optical point of view, is ascertained. The designing calculus of the resulted attenuator is also developed.

Titanium dioxide thin films prepared by sol-gel method and deposited on p-Si (111), n-GaAs (100) and glass have been investigated by Raman spectrometry and photoluminescence analysis. The films were annealed in the temperature range (500-800)°C in air. Raman scattering studies reveal the presence of Raman active modes in the calcinated TiO₂ films related to anatase phase of titania. The photoluminescence spectrum presents prominent red shifted peaks (e.g. at 400 nm for TiO₂/glass), where the maximum is related to the presence in titania films of defect levels corresponding to oxygen vacancies.

Zinc telluride (ZnTe) thin films (d = 0.12 - 1.92 μm) were prepared by vacuum evaporation (quasi-closed volume technique) onto glass substrates. The structural analysis of the films was performed by X-ray diffraction (XRD) technique and atomic force microscopy (AFM). It was found that the films were polycrystalline and have a zinc blende (cubic) structure. AFM images showed that the films have a grain like surface morphology. The values of the absorption coefficient were determined from transmission and reflection spectra. After different heat treatments transmission coefficient strongly decreases. We consider that this effect is due to tellurium excess atoms which diffuse at crystallite boundaries and form microcristallites. Optical energy gap, calculated from the absorption spectra (for allowed band-to-band transitions) was in the range 2.0 eV - 2.2 eV.

The objective of the paper is to analyze, using computer simulation, the thermoelastic generation of ultrasonic perturbations in semitransparent solids when the heat source is a laser radiation. The algorithm, the numerical analysis relies on, will takes into account three main physical phenomena: the absorption of electromagnetic energy in substance with heat generation; thermal diffusion and elastodynamic wave generation by thermoelastic expansion.

Generally, the beam distribution in the tissue in interaction with a pulsed laser is defined by the optical properties (effective scattering and absorption coefficient). A special Er:YAG device used for blood sampling without any pain is presented. Our device emitting on 2940 nm has a special function. It can give four energy levels for four types of skin. At 3000 nm there is an absorption peak in water, and the absorption in tissue is intense and the vaporization is immediate and superficial without surrounding damages. Additionally, the very short duration of the pulse (a few hundred microseconds) avoids the phenomenon of thermal diffusion.

In this paper a simple method for determining the wavelength of an unknown source, (a problem of great theoretical and practical importance), based on the Moire fringes phenomenon and Fourier analysis is presented and put into practice. The accuracy and the simplicity of the problem makes it attractive and competitive.

In this paper a Fourier transform digital holography experimental arrangement is presented. It is actually a hybrid arrangement, half digital half analog. The Fourier hologram was constructed using the analogous means of the so called lensless configuration. The hologram was recorded digitally by a camera with a large CCD array in stead of the recording medium. The recording of the image was analyzed with a computer and the original image was reconstructed by means of the discrete Fourier transform.

The paper presents measurements of magnetic liquids shaping by use of magnetic fields or gravitation and centrifugal forces. These measurements are conducted with the goal of evaluating the characteristics of the magnetic fluids in order to obtain an adaptive system. Values of frequency response domain, pattern imposed configuration response, and free surface curvature were measured. Three types of optical arrangements were used to determine the parameters: schlieren, Fizeau type interferometer and triangulation optical scheme.

There are different methods to obtain nanostructured thin films: chemical, physical, electrochemical, PLD and radio frequency deposition. The aim of this study was to establish the influence of the process parameters on the films structure and to improve the technological parameters. B₂O₃ and P₂O₅ vitreous targets have been obtained to be used as targets for r.f. magnetron sputtering. To obtain high quality targets it is necessary to use p.a. purity reagents which are dry mixed, then melt for 2 hours at 1200-1250°C. The melted mixture is poured in the mould. The vitreous materials are characterized by DTA, chemical analysis and x-ray diffraction to check for stoichiometry. The thin films obtained by r.f. magnetron sputtering have been characterized by AFM and SEM. The thickness of the composite films are "in situ" controlled in the range (2-20) nm. It seems that these films could be used as space layers in magnetoresistive superlattices, in spite these are totally amorphous without separations.

The moiré fringes method and their analysis up to medical and entertainment applications are discussed in this paper. We describe the procedure of capturing 3D images with an Inspeck Camera that is a real-time 3D shape acquisition system based on structured light techniques. The method is a high-resolution one. After processing the images, using computer, we can use the data for creating laser fashionable objects by engraving them with a Q-switched Nd:YAG. In medical field we mention the plastic surgery and the replacement of X-Ray especially in pediatric use.

The goal of the article is to analyze, using computer simulations, the profile of surface and bulk ultrasonic waves generated by pulse shaped sources acting onto the separation surface between metallic and fluid media. It is well known that a short excitation induces on a solid surface, in contact with a gas or liquid, a dynamic displacement whose parameters: amplitude or velocity could be measured using piezoelectric sensors or laser based interferometric devices. However, the internal elastodynamic field inside metallic bodies can not be easily experimentally evaluated, the computer simulations being maybe the only method able to visualize bulk elastic perturbations.

The study of the laser beam is based on optical models, therefore optical models are suited as a tool for study, implement and evaluate the characteristics of an unfocused laser beam. The analysis of the optical models shows the characteristics of pulse and continuous laser beam and the influence over the quality of the industrial process.

A wide range of measurements have been used during time in order to define the characteristics of laser beam, therefore it is useful to analyze and re-establish the role of each type of measurement. The scope of these measurements is to increase the precision and reproducibility with which beams propagate, interact and can be focused on a target (part) in an industrial process.

A novel method is presented for the analytical construction of solitary wave solutions of the nonlinear Kronig-Penney model in a photonic structure. In order to overcome the restrictions of the coupled-mode theory and the tight-binding approximation and study the solitary wave formation in a unified model, we consider the original NLSE, with periodically varying coefficients, modeling a waveguide array structure. The analytically obtained solutions correspond to gap solitons and form a class of self-localized solutions existing under quite generic conditions. A remarkable robustness of the solutions under propagation is shown, thus providing potentiality for various applications.