This PDF file contains the front matter associated with SPIE Proceedings Volume 7142, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. GASMAS combines narrow-band diode-laser spectroscopy with diffuse media optical propagation. While solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures, typically 10,000 times sharper than those of the host material. Many applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. So far molecular oxygen and water vapour have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, allowing propagation. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities have been studied. Transport of gas in porous media can readily be studied by first immersing the material in, e.g., pure nitrogen, and then observing the rate at which normal air, containing oxygen, reinvades the material. The conductance of the sinus connective passages can be measured in this way by flushing the nasal cavity with nitrogen. Also other dynamic processes such as drying of materials can be studied. The techniques have also been extended to remote-sensing applications (LIDAR-GASMAS).

The contribution of Yu.N.Denisyuk, E.Leuth, and Yu.Upatnieks into holographic science and technology is considered from the point of view of the modern state in holography. Some biographical data of these outstanding specialists are given, and their significance in the holography development is estimated.

Multipurpose unified Monte Carlo (MC) based model is developed for adequate simulation of various aspects of optical/ laser radiation propagation within biological tissues. The modeling is aimed to provide predictive information to optimize clinical/biomedical optical diagnostic systems and improve interpretation of the experimental results in biomedical diagnostics. Complex structure of biological tissues in terms of scattering and absorption is presented on the example of human skin. Validation and verification are performed against the tabulated data, theoretical predictions, and experiments. We demonstrate the use of the model to imitate 2-D polarization-sensitive OCT images with non-planar boundaries of layers in the medium like a human skin. The performances of the model are demonstrated both for conventional and polarization-sensitive OCT modalities.

Experimental techniques that exploit pulses of the electromagnetic radiation with characteristic spectra covering the frequency range between few hundreds GHz and few THz and their applications in the characterization of various semiconductor materials are reviewed. The list of material parameters that can be determined by using pulsed THz techniques includes, among other, carrier lifetimes, their energy and momentum relaxation times, inter-valley separation in the conduction band, and nonlinear optical susceptibilities of the material.

We address theoretically adiabatic regime of charge transport for a model of two tunnel-coupled quantum dots connected in series. The energy levels of the two dots are harmonically modulated by an external potential with a constant phase shift between the two. Motivated by recent experiments with surface-acoustic-wave excitation, we consider two situations: (a) pure pumping in the absence of external voltage (also at finite temperature), and (b) adiabatic modulation of the current driven by large external bias. In both cases we derive results consistent with published experimental data. For the case (b) we explicitly derive the adiabatic limit of Tien-Gordon formula for photon-assisted tunneling and compare it to the outcome of simple conductance modulation. A tutorial for adiabatic pumping current calculations with the Green function formalism is included.

Flat panel displays (FPD), flexible electronics and thin-film photovoltaics are booming in the last few years. Permanent annual growth and huge expectations in the market in the near future stimulate the development of versatile technologies for patterning thin-film materials on rigid and flexible substrates. Utilization of laser radiation provides diversity of processing means for structuring deposited films. The high selectivity and diminishing effect on the surrounding material as well as high speed are required in processing complex multilayered systems in the thin-film photovoltaics. Organic electronics imposes special requirements on the geometrical quality of conductors. The current situation with laser direct writing of thin-films in the production of FPD and solar cells as well as our results are presented. High repetition rate lasers with a short pulse duration offer new possibilities for high efficiency structuring of conducting, semi-conducting and isolating films. Laser structuring with the picosecond and nanosecond pulse duration was applied in shaping the thin films deposited on polymers and glass substrates. Absorption of laser radiation by the film material was essential to initiate its controllable removal. Use of UV laser radiation with fluences close to the ablation threshold made it possible to minimize surface contamination and the recast ridge formation during the ablation process. The flexible technique of patterning was applied in prototyping the components for the OLED matrix, RFID antennas and the thin-film solar cells. Well-defined shapes of isolating trenches and conductor lines were produced by laser ablation with the picosecond pulse duration.

Upconversion characteristics of rare-earth cations were utilized for emitting or controlling visible light with infrared light. A fluorescent glass rod was fabricated by using durable AlF₃-based glass that contained high-concentration Er³⁺ cations. This glass rod acted as a two-way wavelength converter; i.e., visible light (~500 nm) was converted to infrared light (~800 nm) as it passed through the glass, and infrared light that propagated in the opposite direction was converted to visible light. An infrared-responsive photochromic compound was fabricated by dispersing spirobenzopyran and upconversion powder (Gd₂O₂S:Yb³⁺Er ³⁺) in photocurable acrylate. When this compound was exposed to ultraviolet light (~370 nm), a strong absorption band appeared in the visible spectral region due to photochromic isomerization of spirobenzopyran. This absorption band disappeared by irradiation of a 940-nm laser beam, since the upconversion powder emitted green light that caused bleaching of colored spirobenzopyran.

Even small fluences of implanted ions used for opto-doping alpha-quartz lead to amorphization of the matrix, but subsequent annealing in air or oxygen can restore its crystalline order (chemical epitaxy). Here we report on cathodoluminescence (CL) spectroscopy during chemical epitaxy of alpha-quartz irradiated with 50-keV Na-ions or 175-keV Rb ions and annealed in ¹⁸O₂-gas. In particular, the variation of the CL spectra with the ion fluence will be discussed. The CL spectra at 10 K show an intense 2.90-2.95 eV blue band and differ greatly from the ones taken at 300 K. Finally we report on the observation of a spider-web surface structure after Rb implantation and annealing in lowpressure oxygen.

Inorganic glass is material having nanoscaled physical and chemical inhomogeneities ad initio because glass inherits thermodynamic fluctuations of concentration, density and anisotropy of a glass forming melt. Combining light scattering and high temperature acoustics data allows to use the effect of internal immersion for designing multicomponent glasses with Rayleigh scattering losses lower than those of the silica glass. Non-random spatial distribution of dopants including rare-earth (RE) ions in a glass host (doped ion segregation) causes excessive Rayleigh scattering losses and enhancement of RE ion-ion interaction. Therefore, it opens the way to optimize operation parameters of laser and up-converting glasses by the proper choice of glass host composition. Results of Raman scattering spectra processing and characterization of electrooptical (EO) sensitivity of niobate glasses showed the existence of groups with stoichiometry of the well-known EO crystals and crystal-like orderliness (crystal motifs) in the glasses as the necessary condition of high EO sensitivity. It was found that EO sensitivity of glasses could be essentially increased by thermal treatment.

Vibrational and structural properties of Ge_xSb_{40 x}S₆₀ (x = 25, 27, 35) chalcogeide glasses are studied in unmodified and γ-radiation-modified states by using infrared spectroscopy, high-energy synchrotron x-ray diffraction and extended x-ray absorption fine structure spectroscopy. An agreement between radiation-induced structural changes and vibrational properties measured is established. It is suggested that the atomic pairs with wrong coordination created in the framework of coordination topological defect formation concept play a key role in the formation of radiation-modified state of the investigated glasses. Advantages and disadvantages of post-technological radiation-modification of chalcogenide glasses are considered within configuration coordinate model for description of unmodified and radiationmodified states.

Millimeter wave bridge technique for non-destructive material homogeneity characterization is described. The idea of this technique is the local excitation of the millimeter waves in the testing material and the measurement of the transmitted (reflected) wave amplitude and phase in different places of it, i.e. the material plate is scanned by the beam of the millimeter waves. Same results of the homogeneity measurements for dielectric wafers according to dielectric constant anisotropy are presented. The measurement technique sensitivity is discussed.

The article examines the processes of second harmonic generation (SHG) when selenium-metal (Cu) film structures are illuminated by femtosecond radiation (180 fs, 80 MHz) at wavelength 800 - 1000 nm. Selenium-copper structures were obtained by successive thermal evaporation of selenium and copper onto the glass substrate in vacuum. Microanalysis of the film composition was performed to determine amount of copper in thin films. The as-evaporated selenium-copper structures were crystallised by annealing in inert atmosphere at temperature 85°C. Just evaporated as well as annealed thin films were explored. The experiment was performed by confocal microscope [1] where the femtosecond radiation from laser was injected. A photosensitivity of structures in question was then determined as functions of intensity and wavelength of the incident radiation [2]. Second harmonic intensity dependence on thickness of Cu layer was also observed. We found out that adding small amount of Cu increases reflected SH intensity.

The photoluminescence (PL), its excitation (PLE) and absorption spectra in ultraviolet, visible and infrared (UV-VIS-IR) regions were used to investigate the MgO single crystals irradiated by fast neutrons. It is shown that the photoluminescence band of the MgO crystals at 730 nm belongs to the hydrogen-containing complex centers V^-_OH-Fe³⁺, which are transformed during the irradiation with fast neutrons. The behavior of the PL band 730 nm after fast neutron irradiation depends on the iron-chromium concentration. It is found that the fast neutron irradiation produces the interstitial proton H⁺_i and the Mg(OH)₂ microphase.

Results of second harmonic (SH) generation in amorphous and crystalline selenium films induced by titanium-sapphire femtosecond laser (wavelength λ - 800-1000 nm) are presented. It is found that the highest intensity of SH is provided by fundamental wave at wavelength 1000 nm and it reaches maximum in approximately 100 sec. The intensity of transmitted SH depends on film thickness while that of reflected does not.

We report the optimization of a tunable source of near-infrared radiation based on a multigrating periodically poled lithium niobate (PPLN). The pump source for the PPLN optical parametric oscillator (OPO) was diode pumped Qswitched nanosecond Nd:YVO₄ laser emitting the radiation at 1064 nm with the pulse repetition rate from 0.2 kHz to 40 kHz. The influence of the output-coupler and the resonator length on the efficiency of the PPLN OPO was investigated. For this aim eight mirrors with different reflectance were tested. A minimum threshold of 30 μJ was measured. The highest output power was 660 mW at 1.64 μm when the pump power was 3 W at 15 kHz pulse repetition rate. The bulk grating periods of the PPLN structure determined the signal in the range of 1.49-2.1 μm and idler in the range of 2.1-3.8 μm.

High power white light emission diode reliability and aging processes have been investigated. Optical, electrical and noise characteristics have been carried out for initial devices and during their aging. Analysis of noise characteristics help revealing of light emission diode aging processes and reliability problems. It is found that optical and electrical noise spectra changes reflect light emission diode aging. Noise characteristics, especially correlation factor between optical and electrical fluctuations, and current-voltage characteristics at low bias reveal physical processes that take place during investigated device aging and rapid its degradation. It is shown that reason of high power light emission diode degradation is related with defects presence in the device structure. Additional defects appear during LED operation and lead to the leakage current and non-radiative recombination increase.

Self-mixing interferometry is a promising technique for a variety of measurement applications. Using a laser diode with an external cavity as interferometer, the technique offers several advantages over traditional interferometric configurations. This research used a self-mixing interferometer built in our own laboratory. It is based on a blue emitting GaN laser diode with a wavelength of 405 nm. Light is directed through an optical fiber from which a 1-cm section of cladding has been removed, and a cuvette for holding the sample is fixed around this part. Interference patterns, created in the laser cavity, are acquired with a computer-based data acquisition system and later processed using Matlab software. Since samples with different refractive indices create interference patterns with different phases, even small changes in sample concentrations can be measured. However, coupling light into a single-mode optical fiber is a very challenging task, and the setup is very sensitive to external interference like airflows or vibrations. Experiments with the device showed that, in stability measurements, the standard deviation of the recorded fringe pattern shifts was only 1.7 nm. In sample measurements, the refractive index change in the sample chamber varied from 1.0029 to 1.33, corresponding to a fringe pattern shift of 297±4 nm.

In this work we present measurement and results of the deconvolution of the Hg 253.7 nm spectral line shapes, emitted from the mercury isotope high-frequency electrodeless discharge lamps, made at the Institute of Atomic Physics and Spectroscopy for the use in Zeeman Atomic Absorption Spectrometry. The emission line profiles of 254 nm Hg resonance line have been measured by means of a Zeeman scanning spectrometer at the mercury cold spot temperature value at 20 C. Then the deconvolution procedure or solving of this ill-posed inverse problem by means of the Tikhonov's regularization method [1] was performed to obtain the real spectral line shape.

In this paper the influence of TiO₂/polymer (RR-P3HT) interface to photo generated charge carriers separation and recombination have been studied. The quantum efficiency and charge carrier recombination were studied in heterojunctions of TiO₂ (prepared with porous or flat interface) and spin coated RR-P3HT polymer film using time of flight (TOF) and double injection (DoI) transient methods. From the shape of the TOF transients it was determined that the charge carrier generation is taking place in the vicinity of the TiO₂/P3HT interface. Samples with porous TiO₂ films show better charge carrier separation, but the deep trapping of charge carriers at the interface appear. The charge carrier recombination is trimolecular (Auger type recombination) with the similar values of recombination coefficients in both types of samples.

Lead salt materials are of high interest for midinfrared optical emitters and detectors for molecular spectroscopy. The IV-VI narrow gap semiconductors have a multivalley band structure with band extrema at the L point of the Brillioun zone. Due to the favorable mirrorlike band structure, the nonradiative Auger recombination is reduced by one or two orders of magnitude below that of narrow gap III-V and II-VI semiconductor compounds¹. The photoluminescence in the midinfrared range for PbSe film structures, excited by a semiconductor laser diode, is investigated. The PbSe films were prepared by Physical Vapor Deposition (PVD) using an electron gun. A PbSe crystal doped with 0.1 at% Bi was used as a source for the fabrication of thin layers. Starting from the assumption that the rate of nucleation is a predominate factor in determining grain size, thin films were fabricated on substrates that had been maintained at various temperatures of deposition process². Amorphous glass and Kapton polyimide film was used as substrate. The growth rate was 0.2 nm/s. Films were thermally treated at high oxygen pressure in a heated encapsulated system. Microstructure has been studied using XRD, AFM and HRSEM. For PbSe structures photoluminescence at temperature as high as 300 K is demonstrated.

The review of results of submicron surface layers formation is presented under ultraviolet (UV) N₂ - laser (λ = 0.337 μm, t_p = 5 ns) ablation of silicon target in liquid environment C₆H₅CH₃. The morphological and deformation state of a near-surface Si layer was investigated by polarization modulation spectroscopy (PMS), atom force microscopy (AFM) and Raman spectra methods before and after irradiation. After irradiation AFM data shows the formation of submicron structures with hexagonal-like type of regularity on Si surface, PMS spectra indicates the increasing of refractive index, Raman spectroscopy reveals the broad band in the range 740-800 cm^-1. All that facts allow us to assume the possibility of SiC-like layer formation on silicon monocrystal surface by laser stimulated diffusion of carbon atoms from liquid media. The surface morphology and composition of the irradiated surface varies considerable with the number of laser shots.

We present experimental study of photoresponse in small area GaAs/AlGaAs heterojunction planar detector induced by nanosecond CO₂ laser pulses. This device revealed itself as a fast IR sensor operating at room temperature. Hot carrier effects are proposed to be responsible for the photoresponse formation.

We demonstrate a novel application of time-resolved transient grating technique for determination of deep trap occupation ratio in semi-insulating crystals. Light diffraction kinetics on a transient reflection grating with very small period (150 nm) provided conditions for studies of absorption nonlinearity and its discrimination from the coexisting free carrier and electro-optic ones. By numerical modeling of absorption grating kinetics in subnanosecond time domain, we determined the contributions of the recharged deep traps and two-photon absorption to diffraction kinetics and evaluated in this way the deep trap compensation ratio in differently grown GaAs crystals. Moreover, the decay time of the absorption grating provided the rate of carrier capture to these dominant deep traps, which have been recharged under illumination. Using this feature, we were able to monitor the thermal annealing process in vanadium-doped CdTe crystals: it has not effected the charge state of vanadium related deep traps, but reduced the concentration of the active residual carrier capture centers in the crystal.

AlGaN alloy thin film materials are of high interest for light emitting diodes (LED of the ultraviolet (UV) spectral region. Origin of the deep intrinsic and impurity Si states in the Al_xGa_1-xN (0 < x < 0.35) epilayer structures grown by metalorganic chemical vapor deposition (MOCVD) technique have been considered. Effects of the lattice mismatch and Si-doping in the heterostructures of epilayers with different alloy composition are investigated using time resolved photoluminescence (PL) of donor - deep acceptor (DA) pairs. It is shown that the undoped AlGaN alloys, grown on a GaN buffer layer, due to the lattice mismatch contain the increased concentration of cation vacancy (V_cation) defects acting as a deep acceptor centers and responsible for PL. Si-doping results in both the additional increase of V_cation concentration and the formation in cation sub lattice of new (V_cationSi_cation) deep acceptor complexes. It is shown that by increase of the Al content in the AlGaN alloy the composition disorder of both deep acceptor centers V_cation and (V_cationSi_cation) complex appears. The corresponding broad PL bands are resolved in number of subbands. It is stated that deposition of Si-doped AlGaN alloy on undoped GaN results in formation of Si-doped GaN interlayer.

Thin films of tungsten oxide (WO₃) have been grown by hot-filament metal oxide deposition (HFMOD) technique under atmospheric pressure and an oxygen atmosphere on glass substrates. The thin film of WO₃ has been extensively studied as an electrochromic material and has numerous applications in electrochromic devices. In order to explore the possibility of using WO₃ in electrochromic devices, a preliminary and thorough study of the structural and optical properties of the host material is an important step. By the X-ray diffraction analysis the single phase natures, monoclinic and orthorhombic structure of the films have been confirmed. The IR spectra were constituted of many broad peaks in the 1400-3500 cm^-1 region That are assigned to ν(OH) and δ(OH) modes of adsorbed water. The corresponding WO₃ vibrations are in infrared regions of 1453-400 cm^-1 and 3454 cm^-1, which correspond to W-O stretching, bending and lattice modes. By Transmittance measures determines that the optical bandgap is around 2.92 eV. We have observed that the good quality WO³ thin films can be satisfactorily grown by this technique.

The quaternary alloy In_xGa_1-xAs_ySb_1-y highly doped with tellurium was grown on substrates of p-type GaSb in the direction (100) by liquid phase epitaxy (LPE). The longitudinal (LO) and transverse (TO) optical modes were obtained using the modified random-element iso-displacement model (MREI model). The comparison of the experimental results with obtained by the MREI model allows to confirm that the bands correspond to the modes associated LO and TO of the binary compounds GaAs and (GaSb + InAs).

Raman studies of ostensibly pure congruent, close to stoichiometric and stoichiometric lithium niobate single crystals and single crystals of lithium niobate containing admixture of Gd³⁺, Y⁺, and Mg²⁺ are reported. The authors have revealed weak Raman bands anomalously narrowing at changes of crystal composition disordering the cation sublattice and discuss the results with regard to evidence of anomalous ordering of structural units of the cation sublattice occurring at disordering of the cation sublattice as a whole.

In this work we present an interpretation of experimental O K-edge x-ray absorption near edge structure (XANES) in perovskite-type WO3 and AWO3 compounds (A = H and Na) using three different first principles approaches: (i) fullmultiple- scattering (FMS) formalism (the real-space FEFF code), (ii) hybrid density functional theory (DFT) method with partial incorporation of exact Hartree-Fock exchange using formalism of the linear combination of atomic orbitals (LCAO) as implemented in the CRYSTAL code; (iii) plane-wave DFT method using formalism of the projectoraugmented waves (PAW) as implemented in the VASP code.

Stimulated emission dynamics in InGaN-based multiple quantum wells (MQWs) is analyzed. The lasing threshold measurements of the In_0.09Ga_0.91N/In_0.02Ga_0.98N MQWs revealed non-monotonous threshold dependence on the growth temperature of the active MQW region. The optimal growth temperature range with the lowest stimulated emission threshold (100 kW/cm²) in the active region was found to be 780 - 800°C. The influence of indium nano-clusters on stimulated emission threshold is discussed. Optical gain in InGaN MQWs was measured using variable excitation stripe length technique. The optical gain dependence on excitation stripe length and excitation power density was studied. The onset of the gain saturation was observed on the high energy side of the stimulated emission peak. The onset exhibited red-shift with increasing stripe length due to reduced electron-hole density caused by high optical transition rate. Increase of excitation power density resulted in the strong blue-shift of the optical gain spectra. The maximal optical gain coefficient values of 200 cm^-1 and 300 cm^-1 were obtained for the samples with the lowest and the highest stimulated emission thresholds, respectively. The calculated optical confinement factor (3.4 %) for the samples yielded the net gain coefficient of about 5900 cm^-1 and 8800 cm^-1, respectively

We report preparation and properties of hybrid bilayer structures composed of the organic semiconductor, 8-hydroxyquinoline aluminum (Alq3), p-type Si and two ferromagnetic oxides, namely, colossal magnetoresistance manganite, La_2/3Sr_1/3MnO₃ (LSMO), and magnetite (Fe₃O₄). Thin Alq3 films were thermally evaporated in vacuum. The bottom LSMO films were grown in-situ at 750°C by dc magnetron sputtering on crystalline SrTiO₃ while Fe₃O₄ films were magnetron sputtered at 400°C on glass. Current versus voltage in a case of vertical current flow has been investigated for the heterojunctions. The investigations revealed dominating role of thermoionic emission in a barrier of Schottky type for the Alq3/p-Si heterojunction while a mechanism based on carrier tunnelling through an interface and space charge limited current processes were considered to explain nonlinear electrical transport in the Alq3/LSMO, Alq3/ Fe₃O₄ heterojunctions. The Alq3/LSMO demonstrated magnetoresistance values up to 11 % (at T=240 K and B=1 T).

We report the experimental data of typical liquid crystals (6CHBT and w1680) in the nematic phase doped with and without Sudan dyes. We investigated the effect of an ac-applied voltage on the nonlinear behavior of dye doped liquid crystal (DDLC). The z-scan technique is used to measure the amplitude and the sign of the nonlinear refractive indices DDLC. The amplitude of negative nonlinear refractive indices was (~10^-5cm²/W). The nonlinear absorption coefficient β of DDLC was measured by using open aperture z- scan technique. Also the optical limiting (OL) response of DDLC was obtained. The novel effects on the far-field diffraction patterns of a Gaussian beam were depended on the external applied field. The measurements were performed using a CW He:Ne laser and CW Nd:Yag laser tuned at 632.8 nm and 532 nm, respectively. Also Gaussian beam propagated through a thin cell (sample thickness =11.8 μm).

In connection with 60th anniversary of new optical division - holography - the significant changes are considered which occurred due to holography in the area of recording and storage of information carrying by light. New recording media are discovered, and some old recording media are significantly improved, new recording methods of light information recording and storage are proposed. It is noted that despite the prominent achievements, a very wide work regarding holographic information recording and storage media and methods lies ahead in order to realize the possibilities of holography more completely.

Two important features make a holographic system more substantial than an ordinary optical system: ability of phase information transmission (on a level with amplitude one) and ability of the separable overlapping of wavefronts from different objects. However, holographic signal is more complicated than that transmitted by ordinary optical devices. Due to this the statements of information theory require some modifications in a higher degree for holographic systems than for optical ones in order to provide the information transmission description.

The holographic recording efficiency in doped LiNbO3 crystals has been studied both experimentally and theoretically depending on the type of dope, on the recording geometry and on the polarizations of the recording and readout light.. The studied crystals can be arranged in the following order by their efficiency: LiNbO₃:Cu, LiNbO₃:Fe (yet having a smaller thickness and donor concentration than LiNbO₃:Cu), LiNbO₃:Fe+Cu, LiNbO₃:Fe+Ti, LiNbO₃:Ti. It was found that the recording geometry with the holographic grating vector along the optical axis is much more efficient than in the perpendicular configuration.This fact is in accordance with the photorefraction theory based on photogalvanic and linear electro-optic effects (PGE-LEO theory). Other recording mechanisms are active, too, but much less eficient. The recording efficiency polarization dependence is mainly determined by dopes.It is different in the cases of Fe and Cu impurities. It also follows from our studies that photoconductivity along the optical axis is much larger than in the perpendicular direction.

The researches of the possibility of Au nanoparticles formation in conditions of surface plasmon resonance (SPR) at irradiation of the Au film / glass structure by YAG:Nd⁺³-laser nanosecond pulses of the p-polarization (t_p = 10 ns) by fundamental (λ = 1.064 nm) and second harmonics (λ = 0.532 nm) are submitted. The morphology of an Au film surface before and after laser action, Au fragments sizes and their surface distribution were investigated by the atom force microscopy (AFM). The effect of Au nanoparticles formation was observed only at the second harmonic irradiation (λ= 0.532 μm) in SPR conditions in the Kretschmann configuration. The considerable difference between the average Au nanoparticles sizes δ created at the SPR conditions, R = R_min, δ ~ 80 nm that was obtained in the case out of SPR R≠R_min δ ~ 1350 nm is established. Threshold energy density of micro-ablation P_thn is determined, that one in the case of SPR P_thn ≈ 5.5 J•cm^-2 was essentially lower than in the SPR absence, P_thn ≈ 8 J cm^-2. The histogram obtained on the AFM data has shown a high degree of the height sizes homogeneity of Au nanoparticles. Under the AFM data a conclusion about the determining contribution of the plasmon - polariton subsystem in formation process of Au nanoparticles in SPR conditions at high levels of laser irradiation was made.

We have performed the investigation of dot matrix holographic recording in amorphous As₂S₃ chalcogenide films with different thickness on Al coated glass substrates. The control over the interference minimum of reflection during the evaporation process allowed obtaining As₂S₃-Al system with a minimum value of initial reflection in defined spectral region. The investigation of dependence of diffraction efficiency of holographic recording on both film thickness and initial conditions of reflectivity in the system was performed. The main advantage of this type of system is the possibility to increase optical sensitivity of material in predefined spectrum region for phase hologram recording.

Recently a number of organic and inorganic materials have been studied for direct surface-relief formation during the exposure process by a light or e-beam. It is very promising for practical application enabling the possibility to simplify the surface-relief formation technology. In this report the method of preparation of thin polymer-chalcogenide and polymer-azobenzene composite films is described, and some features of photoinduced changes of optical properties and holographic recording of these materials are studied. Films of composites were obtained from solution of arsenic sulphide, Disperse red 1 and polymers in organic solvents. The solution was spread on glass substrate and dried. The dry film thickness was in the range of 3-10 μm, with different correlation of arsenic sulphide, Disperse red 1 and polymers. The absorption spectres of these films was studied and described. The holographic recording of diffraction gratings was performed by different laser lines (442, 532 nm). During recording the diffraction efficiency was measured simultaneously in transmission and reflection mode. The profiles of the gratings and expositing area were analyzed by AFM microscope. Microanalysis of exposed and unexposed films showed a difference in chemical composition that can be explained by transfer of matter under the action of light.

The laser photoacoustic spectroscopy (LPAS) can be applied analytically to determine the concentration of an analyte in samples and its absorption variation as a function of time. The LPAS has advantages of higher detection sensitivity, pure absorption measurement and much less interference by background scattering in comparison with traditional optical spectroscopy. On the other hand, the apparatus is simpler and more generally useful than that of fluorescent spectroscopy. In this study, we built a photoacoustic setup of a Q-switched Nd:YAG laser excited at the third harmonic wavelength and a wideband piezoelectric transducer clamped to the side of a cuvette. The samples included NADH solutions, mitochondrial suspensions and Intralipid-ink mixtures. The experiment results show that the lowest detectable absorption of the setup is in the order of 10^-5 cm^-1; the detectable concentration of NADH in a buffer is as low as 1.67 μM. When monitoring mitochondrial suspensions, the minimal concentration that can be detected is lower than 0.1 mg/mL and the absorption variation caused by full reduction of NAD+ to NADH in mitochondria can be detected.

Confocal micro-Raman and FT-IR spectroscopies have been used for detection of radiation influence of hemoglobin of patients examined by radio-isotopes diagnosis (Tc^99m). After irradiation we observed some little changes of the Raman scattering bands which connected with out of plane porphyrine bending vibrations, also we observed additional band due to methemoglobin. Radiation of blood lead to the transition from hemoglobin (Fe²⁺) to methemoglobin (Fe³⁺) with a delocalization of iron from porphyrine plane. It was shown that FT-IR spectra indicate the radiation effects on hemoglobin.

The experimental studies of the rough surface profile are described. These studies have been performed using acoustooptic tunable filters and optical components with strong chromatic aberration. The basic characteristic of the surface profilometer mock-up is longitudinal resolving power (by z-distance) which has to be defined according to the certain criterion. The proposed criterion is connected with the probability of missing of information unit which relates to the z-distance characterization of the device. The experimental circuit providing the surface profile measurements is described, and the experimental results are listed and discussed. The most interesting result is that defocusing is distinguished with 90% probability at electric frequency deviation of 200 kHz. The perspectives of the further improvement of information transmission by this device are discussed. It has been found that this improvement can be attained by means of the noise level decreasing to the level taking place for electric frequency of 94 MHz.

In routine eye examination the visual acuity usually is determined using standard charts with black letters on a white background, however contrast and colour are important characteristics of visual perception. The purpose of research was to study the perception of isoluminant coloured stimuli in the cases of true and simulated amlyopia. We estimated difference in visual acuity with isoluminant coloured stimuli comparing to that for high contrast black-white stimuli for true amblyopia and simulated amblyopia. Tests were generated on computer screen. Visual acuity was detected using different charts in two ways: standard achromatic stimuli (black symbols on a white background) and isoluminant coloured stimuli (white symbols on a yellow background, grey symbols on blue, green or red background). Thus isoluminant tests had colour contrast only but had no luminance contrast. Visual acuity evaluated with the standard method and colour tests were studied for subjects with good visual acuity, if necessary using the best vision correction. The same was performed for subjects with defocused eye and with true amblyopia. Defocus was realized with optical lenses placed in front of the normal eye. The obtained results applying the isoluminant colour charts revealed worsening of the visual acuity comparing with the visual acuity estimated with a standard high contrast method (black symbols on a white background).

Eye movement research of reading has been done on a battery of eye-tracking setups during last decades. We compared reading data of the same group of six students, their eyes were tracked by a video-based helmet-mounted system with the data sampling frequency of 50 Hz and a setup with a chin-rest at 240 Hz. We found that not only the number of fixations may decrease after reading practice, but so does also the mean duration of fixations. In spite of the short duration of saccades, their distributions and changes in them are similarly reported in the two experimental conditions. Lack of significant correlation in the HED data testifies to the result variability due to measurement technique. We conclude that the head-free setup is applicable in reading research but has insufficient precision to track changes in reading patterns.

The minimum average optical signal power, P_min., in optical communications is limited by the photodetector quantum efficiency and by noise. In this paper, the effect of thermal photons irradiated by all materials at absolute temperatures T>0 on optical information detection in communication lines is quantitatively considered. Usually, only the thermal current fluctuations in the photodetector are taken into account. Basing on the negentropy principle of information, assuming the Planck's blackbody radiation spectral distribution of photons, and describing the optical communication channel as non-symmetric noisy binary channel we have calculated the minimum energy required for the detection of one bit of information, ε= 6.5kT/bit, k =1.38×10^-23 J/K being the Boltzmann constant. This ε value corresponds to the large error probability q = 0.20. At T = 20°C ε=4.05×10^-21 J/bit and for the bit rate of R = 10¹⁰ bits/s one finds P_min = R_ε2.63×10^-7 mW. In the case of more realistic value of q=10^-9 ε=26kT/bit=1.05×10^-19 J/bit, P_min = 1.05×10^-6 mW. This is only about 10 times lower than the quantum photodetection limit of conventional photodetectors. For more sensitive photodetectors the thermal photon noise can become important. It is shown that the minimum signal energy estimate ε≈10^-19 J/bit is applicable also in a wider error probability range of q=10^-3-10^-15.

Research of eye movements in reading textbooks suggests that reading the Cyrillic-based Russian language differs from reading the extended Latin-based Latvian texts. Ten bilingual students were asked to start reading a book passage in Latvian and to continue reading the text in Russian. Key parameters in information processing have been analyzed. Even though the difference in duration of fixations does not reach statistical significance, saccade size and regression rate are smaller in Russian.

Important optical parameter of the eye is intraocular light scattering. Straylight can reduce visual acuity, contrast sensitivity. It is one of the main factors for glare, especially for drivers at night, when there is light source some distance away from the fixation point. There are many factors, which can affect amount of light scattering in the eye. To assess the effect of the color of the straylight source on retinal image quality at different light scattering levels, retinal straylight was measured with and without light scattering occluder. Red, green and blue colors were choosed for straylight source. Psychophysical and electrophysiological methods were used to evaluate light scattering effect on perception on different color stimuli. Results show that straylight values are the greatest for blue color with and without light scattering occluder. In measurements without light scattering occluder ratio of straylight values for red and green color are different between subjects. Using light scattering occluder straylight values for green color are greater than for red color. Optical and anatomical factors which can induce these spectral variations are discussed. Psychophysical and electrophysiological methods showed the similar changes in results with straylight values when light scattering were increased.

In pediatric ophthalmology 2 - 3 % of all the children are impacted by a visual pathology - amblyopia. It develops if a clear image isn't presented to the retina during an early stage of the development of the visual system. A common way of treating this pathology is to cover the better-seeing eye to force the _"lazy" eye to learn seeing. However, children are often reluctant to wear such an occluder because they are ashamed or simply because they find it inconvenient. This fact requires to find a way how to track the regime of occlusion because results of occlusion is a hint that the actual regime of occlusion isn't that what the optometrist has recommended. We design an electronic eye occluder that allows to track the regime of eye occlusion. We employ real-time clock DS1302 providing time information from seconds to years. Data is stored in the internal memory of the CPU (EEPROM). The MCU (PIC16F676) switches on only if a mechanical switch is closed and temperature has reached a satisfactory level. The occlusion is registered between time moments when the infrared signal appeared and disappeared.

Amorphous chalcogenide thin films are excellent materials for holographic recordings. AsSeS thin film coating is a useful optical material for it's thickness to be easily corrected with the use of exposure to light and consecutive chemical etching. Following properties allow to treat the surface of AsSeS chalcogenide films and to use them in adaptive optics systems for correction of the optical wavefront. Hereby, we characterize AsSeS film properties to be used for correction of optical aberrations of the human eye. The thickness of the film is characterized with the method of spectrodensitometry and the surface profile depth with a Hartman- Shack waveform analyzator.