Organic molecular materials displaying effective optical second harmonic generation (SHG) is of major interest in molecular engineering and non-linear optics. In this review synopsis of experimental and theoretical studies of photoactive molecular multilayer Langmuir-Blodgett (LB) films of oriented dipolar betaine type organic molecules is presented and the pathways of search of new indandione-1,3, pyridinium betaine (IPB) derivatives with enhanced second- order non-linear response are discussed. Characterization of highly dipolar betaine-type molecules, with IPB molecule as a prototype, has been presented and conditions of effective SH generation discussed. Molecular structure, phase transitions and optical properties of monolayers of amphiphilic IPB derivatives on the water/air interface have been discussed. Electronic and both linear and non-linear optical properties of LB multilayer molecular assemblies of amphiphilic IPB derivatives have been discussed. New developments in molecular engineering in search for new molecular compounds with high SHG response have also been briefly discussed.

The research objects are bipolar organic compounds containing both charged electron donor and electron acceptor groups interconnected with some kind of bridges ^-D-X- A ⁺. Such types of compounds are named as betaines and the betaines are peculiar for photoinduced intramolecular electron transfer (PIET), a large change of the dipole moment in the exited state and a considerable hyperpolarizability which causes large nonlinear optical effects in solutions and LB-films. The quantum chemical calculations (CNDO/S) of some types of betaines containing, 1,3-indandione anion or diazole anion electron donor part and N-pyridinium cation electron acceptor part show that the HOMO and LUMO are strongly localized and an effective PIET takes place. The calculated change of the dipole moment in the exited state, (Delta) (mu) equals (mu) _g-(mu) _e, is essential (8-20 D) and in many cases the direction of (mu) changes to opposite. The character of the bridge X in betaines shows the largest effect on (mu) _g and (Delta) (mu) especially in the case of X equals p - phenylene. The pyrazole anion part is a better electron donor than the 1,3- indandione anion. These are synthesis of betaines containing the 1,3-indandione anion part and the N-pyridinium cation part interconnected directly or through p-phenylene bridge has been fulfilled and the electron absorption spectra have been investigated. The preliminary experiments confirm NLO effects in solutions and LB-films. The synthesis of novel substituted betaines is unlimited, synthesis of polymer- bonded or surface-bonded betaines is possible.

In this paper nonlinear optical properties of indandione-1,3 pyridinium betaine (IPB) molecule and its novel amphiphilic derivatives have been studied. Hyper-Rayleigh scattering (HRS) has been used as a direct and accurate tool to determine effective hyperpolarizability (beta) of IPB derivatives dissolved in chloroform. Evaluation of hyperpolarizability gives an averaged values of (beta) from 140 multiplied by 10^-30 to 450 multiplied by 10^-30 esu. Disordering of molecular orientation for multilayer Langmuir-Blodgett films of compound C₁₇-IPB has been studied by SHG techniques and discussed for different film thickness. It has been observed that orientation degree of the Z-type molecular structure increases significantly with the thickness of deposited LB film.

The origin of the excited states and the spectroscopic features of polar molecular films and crystals of N,N- dimethylaminobenzylidene 1,3-indandione (DMABI) was considered. The formation of charge transfer exciton states in the absorption and luminescence spectra by increase of the thicknesses of DMABI films was observed. The evidence of a strong exciton-phonon interaction and its effects on the exciton absorption and luminescence spectra was discovered. The coexistence of free and self-trapped excitons at elevated temperatures was found in DMABI films. The dynamics of both shallow short-lived and deeply trapped long-lived self-trapped exciton states in various films and crystal of DMABI was discussed.

Molecular structure and optical properties of the novel amphiphilic derivative of dimethylaminobenzylidene 1,3- indandione (C17DMABI), have been studied as the monolayer on a water surface (Langmuir films) and Langmuir-Blodgett (LB) multilayers of Y-type structure using optical absorption techniques. The compression (pi) - A isotherms of the C17DMABI monolayer show two different phases. Phase transition takes place at surface pressures 1 less than (pi) less than 20 mN/m. The compression-induced changes of the monolayer spectra in the region 330 - 600 nm have been analyzed using deconvolution of spectra of Gaussian shaped bands. At least three different transitions takes place at approximately 395, approximately 445 and approximately 505 nm. Analysis of deconvoluted band spectral shifts, intensities and dichroism confirms a molecular packing rearrangement and change of the tilting angle at the phase transition pressure interval.

Time resolved photobleaching studies of titanyl phthalocyanines with different crystalline structures are reported. Strong photobleaching of the edge components of the complex Q absorption band and much weaker in the center of the band was found to be a general feature of crystalline and amorphous structures. Such behavior was explained by the ultrafast excitation transfer between different molecular species.

Different factors controlling the linear and nonlinear optical (NLO) properties are discussed for conjugated organic materials having linear chain or ladder structure. It is shown that one-dimensional conjugated molecules reveal similar values of hyperpolarizability as molecules with ladder structures having the same geometric length. After normalizing the value of third order nonlinear response to the number of pi-electrons involved, the chain molecules show significantly higher values. The introduction of heteroatoms into the conjugated part of molecules or linking pendent groups to them are efficient means to tailor not only linear but also nonlinear optical properties. One example of heterosubstitution is the introduction of nitrogen into the conjugated main chain which leads to a change of molecular geometry compared to pure hydrocarbon molecules which is connected with a change of absorption and nonlinear optical properties. So azomethine dyes have a blue shifted absorption and lower NLO susceptibility than stilbene dyes. This can be explained by a non-planar structure of the azomethine molecules reducing the overlap of pi-orbitals. A second important modification of optical properties can be reached by partial fluorination of the molecules or by replacing usual acceptors like nitril- or nitrogroups by a trifluoromethyl group. The second order hyperpolarizabilities beta of different fluorine-containing chromophores were determined by solvatochromic measurements. The investigated fluorine-containing chromophores show beta- values as high as standard NLO-dyes like disperse red I but different linear optical properties.

Five amphiphilic alpha- or beta-amino acid derivatives containing photoactive azobenzene moiety and bearing amide or sulfonamide functional groups were synthesized and mono- and multilayers, prepared by Langmuir-Blodgett technique, were investigated. The reversible photoisomerization processes in solutions of these derivatives were observed. Reversible trans/cis photoisomerization of 4-[4-(hexyl- palmitoylamino)- phenylazo]benzenesulfonyl-(beta) -alanine in multilayer assemblies has been observed on alternate irradiation with UV light (centered at 360 nm) and visible light (452 nm).

The present publication is devoted to the studies of the structure of the Langmuir-Blodget films of (methylacylamino)azobenzene derivatives and their electrical properties. Structural studies of monolayer have been carried out by atom force microscopy. The molecules are closely packed in a hexagonal crystalline array. UV irradiation causes a rearrangement of the molecules and a significant structural modification in the monolayer is observed in the frontier region between two crystalline domains of different orientations. The anisotropy of dc conductivity sigma is observed in multilayer assemblies. A low dc conductivity in the bulk sample of the order of sigma_{(perpendicular}) approximately equal to 10^-1010^-13 S/cm is obtained. In the case of in-plane conductivity the value of conductivity is of the order of sigma_(parallel) approximately equals 10^-8- 10^-10 S/cm. The several sets of hole trapping states are situated at energy depth of E_t¹ equals 0.55 plus or minus 0.03 eV and E_t² equals 0.48 plus or minus 0.03 eV with the value of the total density of given set of traps of the order of 10¹² cm^-3. The frequency dependence of capacitance and conductance is nonlinear, with capacitance values decreasing exponentially with higher frequencies while the conductance increases gradually. The behavior is one typical for low mobility materials and the conduction mechanism can be explained in terms of hopping conduction between localized states. The linear dependence of dc in-plane conductivity on relative humidity was observed.

Stable polymer chromophor systems for electro-optical or other nonlinear optical applications can be obtained from dye-containing polyallylic ester polymers by corona poling combined with a simultaneous, thermal or photochemical crosslinking process. Molecular dynamic properties of these materials were observed by thermally stimulated discharge current measurements in order to estimate long-term stability of the orientational state reached after poling and cross-linking. Near glass transition several relaxation processes of the material were detected which influence the over-all relaxation time of the chromophores. The number, temperature position and relaxation strength of the different processes depend on the chemical constitution of the investigated allylic ester polymers. For certain polymers a solid state transformation was observed which can be attributed to a cyclic isomerization reaction. After poling and cross-linking at temperatures between 140 degrees Celsius and 180 degrees Celsius the investigated materials show stable orientation for years below 80 degrees Celsius. This can be concluded from isothermal and thermally stimulated relaxation experiments. In addition, these polymers are excellent film forming materials so that low- loss waveguide structures can be made from these materials either by photolithographic techniques or by molding.

Isocyanates, basic starting materials used in automobile and household paints, are classified as respiratory sensitizers by the UK Health and Safety Executive Commission. There are several procedures for the determination of isocyanate concentration, in the working environment, including HPLC, HSLC techniques, which are, however, incapable of continuous monitoring of the working environment of an individual worker. The crucial drawback lies in the fact that these methods only produce an average concentration, inhaled by the worker, during the whole sampling period. Instantaneous sharp exposures cannot be identified at any given time interval. This communication describes the fabrication of metal-free phthalocyanine derivative multilayers and their reaction to TDI exposures in a controlled environment. Thin films of a metal-free phthalocyanine derivative, when exposed to 35 ppb of TDI have been observed to produce alterations in their resistance values. Thirty nm films have shown an average maximum resistance change of approximately 2.3 multiplied by 10⁸ (Omega) while films of approximately 90 nm thickness showed a resistance alteration of approximately 1.5 multiplied by 10⁷ (Omega) , when exposed alternatively to the analyte for 2 minutes followed by fresh air for another 2 minutes to flush the system. The average response times have been calculated to be approximately 30 to 40 seconds. The repeated reactions of the samples were quite remarkable since the literature review of known isocyanate reactions does not indicate reversible reactions of this nature.

The photoluminescence of the porous silicon obtained by special procedure with the usage of the chemical and laser beam treatment of silicon crystal was investigated in water, buffer and solution containing sodium chloride. It was demonstrated that the intensity of the photoluminescence did not practically change at the above mentioned conditions as well as after antigen or antibody immobilization on the porous silicon surface. But this parameter of the photoluminescence dramatically decreased in case of specific immune complex formation on the silicon surface. The level of the photoluminescence extinguishing depended on duration and intensity of immune reaction. It is proposed to use discovered effect for creation of the immunosensors based on the direct registration of immunocomplex formation.

A review of the latest advances in the field of investigations and applications of photochromic organic systems with practically acceptable properties only is presented. The analysis of the attained results shows that the development of media for the most-used photochromic light modulators is completed essentially. The development of photochromic recording media for working optical memory remains unresolved. The prospects for the development and application of new organic photochromic systems for these applications are closely associated with advances in solution of the problem of fatigue resistance under prolonged irradiation for modulators and optical memory and long storage in darkness for optical memory. Among the new directions efforts to develop photochromic compounds with polyfunctional properties are noteworthy.

Photochromic materials produced from polymethylmethacrylate lose their photochromic properties through time. It has been discovered that irradiation of such materials resurrects the lost properties completely. The restoration occurs under irradiation with electrons at a fluence of 5.0 multiplied by 10¹¹ cm^-2 or with gamma rays at a dose of 500 Gy. Time-resolved spectroscopy has shown that the photochromic state in the materials arises in less than 5 ns while the return to normal state occurs in 0.5 s.

Optical and sorptive properties of cellulose have been investigated by three methods covering the wide 7000 - 80 cm^-1 spectral range. Attenuated total reflection spectra showed shift of sorbed water bands to shorter wavelengths under paper moisture increase. Surface electromagnetic waves (SEW) propagation at metal - Ge (film) - paper system were investigated firstly in far infrared region. Four slopes in the SEW intensity dependence versus time under paper drying were observed. Near infrared diffuse transmittance revealed a band of bonded to cellulose water at 1.53 micrometers which shows 0.08 micrometer red shift compared to 1.45 micrometer band of free water. Damping constants of cellulose sheets of various thickness were determined in the 140 - 85 cm^-1 range by the surface electromagnetic wave method. Sorptive properties of cellulose are compared to those of other sorbers made of divided silica.

A structure of polymer vacuum coatings deposited on aluminum substrates was investigated by the methods of external and internal reflection IR-spectroscopy. It is shown experimentally that macromolecules of the polymers have primary orientation concerning a plane of a substrate, and this orientation unmonotonity decreases with growth of thickness of films. The sharp reduction of orientation is observed achieving the thickness of a films about 1 micrometer. The concentration of additional chemical groups arising at formation of layers, can be reduced by selection of optimum technological conditions of deposition of films.

We report the results of a study of photovoltage which is generated on p-n and l-h GaAs structures under pulsed infrared laser excitation. The hot carrier photocurrent reaches its maximum value at bias voltage related to potential barrier height of p-n junction. We demonstrate that the photoresponse consists of fast and slow components which result from free-carrier and crystal lattice heating, respectively. The obtained results indicate that nonuniform GaAs structures can be used for fabrication of fast detectors based on free-carrier heating by infrared light.

Quantum well (QW) structures (single QW, superlattices of two-dimensional 2D QW, quantum-roads-1D and quantum dots-QD) as objects for nonlinear optoelectronics have been considered. The low power lasers, as well as other quantum- optical devices, have been studied and analyzed.

Usage of novel high optical quality phosphate glass allows us to produce CdS and CdSe quantum dots with high monodispersity. Thermal processing of the glass leads to growth of formed quantum dots. Complicated structure of optical absorption spectra is observed, and preliminary identification of quantum electron-hole transitions is proposed.

The kinetics of photoconductivity and the spectral photosensitivity of a semiconductor with anisotropic electroconductivity in nonhomogeneous electric field has been investigated. Photoconductivity of germanium samples of ring geometry was studied experimentally and theoretically. The main results are: decay of the photocurrent in a semiconductor in the presence of a transverse gradient of electric field differs from the exponential one and depends on mutual directions of the gradient and the drift of the carriers; a photodetector with parameters reversibly controlled by electric and magnetic fields is possible. It was found that spectral photosensitivity either selective or bolometric depending on mutual directions of incident light, the gradient of electric field, and of drift of carriers.

Results on the influence of annealing in vacuum and in Te vapors to the dark and light resistance's (R_D and R_L) of CdTe:Cl miniature crystals (300 - 400 micrometer) of monograin powders is reported and discussed. The dark to light resistance ratio 10⁵ (R_D equals 10¹¹ (Omega) ) at incandescent light intensity of 10⁴ 1x at room temperature have been obtained for 400 micrometer size CdTe:Cl round-shape monograins. Process of annealing was found to shrink the porous structure of as-grown CdTe monograins and to smooth the crystal surfaces.

ZnO thin films with electrical resistance as low as 10^-3 (Omega) (DOT)cm and transparency of 90 - 95% have been prepared by spray pyrolysis of zinc acetate solutions. However, a careful optimization of all deposition conditions is needed in order to obtain films with these values. Thermal decomposition of precursor, the influence of preparation conditions on the film properties and on the film formation mechanism are studied. The stepwise thermal destruction of Zn(CH₃CO₂)₂(DOT)2H₂O is recorded and it is shown, that single solid phase ZnO is the only decomposition product at temperatures higher than 590 K in air. Three characteristic temperature regions were distinguished in the film growth process exhibiting each a different mechanism of crystal growth and leading to different thin film qualities. The optical, structural, morphological and electrical properties of sprayed films are mainly determined by growth temperature and are in dependence on the concentration of dopants. This can be explained on the basis of changes in the growth mechanisms and chemical purity of the films.

The optical properties of SiO₂-(Co plus Si)-SiO₂-Si structures studied by treatment with Q-switched YAG:Nd and carbon dioxide lasers are presented. The photo-thermo- chemical reaction of Co with Si has a threshold character. No change in optical properties of (Co plus Si) mixture was observed up to 2 MW/cm² intensities of carbon dioxide laser radiation. A decrease of the reflection coefficient R from 70% to 45% is observed as the intensity is increased up to 8 MW/cm². When this multilayer structure is subject to Q-switched YAG:Nd laser radiation of the intensity from 14 MW/cm² to 53 MW/cm², the magnitude of the reflection coefficient returns to its initial value 70%. It means that information recorded by carbon dioxide laser is erased. Calculations of the temperature field during irradiation with carbon dioxide and YAG:Nd laser showed that the phase transition from mixture (Co plus Si) to CoSi₂ caused by carbon dioxide laser irradiation results in recording of information, whereas the thermal impact caused by YAG:Nd laser irradiation results in amorphization of CoSi₂ and erasing of information.

The generation of unstable at room temperature centers in boron-doped Si during laser annealing are under investigation. It is shown, that the generation of two kinds of unstable centers with different recombination time constants during the laser annealing takes place. Through an investigation of dependence of the recombination time constants on temperature the activation energies of these donors are determined: E_F equals 0.8 - 0.9 eV and E₂ equals 1.4 - 1.5 eV. It is detected, that recombination time constants of centers depend on boron and oxygen atoms concentrations in laser-annealed region -- recombination time constants of both kinds of centers decrease with increase of both boron and oxygen concentrations in silicon. It is shown, that the generation of these unstable donors does not occur during the laser annealing of boron-doped silicon with basic frequency of Q-switched Nd:YAG-laser (wavelength 1.06 micrometer). The model of generation mechanism of the donors is proposed taking into account dependence of recrystallization velocity during pulsed laser annealing on absorption coefficient of radiation and a great difference in absorption coefficients of basic (k₁ equals 15 cm^-1) and double (k₂ equals 10⁴ cm^-1) frequencies of Nd:YAG-laser radiation.

Nonalloyed W-Zn compound based ohmic contact to p-type GaAs were obtained by vacuum pulse YAG-laser deposition of W/Zn/W/GaAs structure and by laser stimulated impurity Zn diffusion for forming of the submicron contact structure. Pulse laser modification processes were controlled by the pyrodetector system. High level of impurity concentration N_Zn allowed to form the p⁺-p GaAs layers. The W layers provided the drastic boundaries of contact layers and its thermal stability. The typical R_c value of 2.10^-5 (Omega) .cm² obtained for the W/Zn/W/GaAs remained stable after 400 degrees Celsius annealing and after 150 ma current testing during 100 hours.

The influence of a magnetic field on the polarization characteristics of thermal radiation emitted by isotropic semiconductors was investigated theoretically. It was shown that thermal emission is polarized and the degree of polarization depends on the applied magnetic field and experiment geometry. Muller matrix formalism was used firstly for the decision of such problems.

The influence of low-dose (up to 10 Cl/kg) underthreshold X- irradiation (Cu K_alpha, 20 - 40 kV, 20-40 mA) on physical parameters of surface-barrier diode structures Au- ZnS has been investigated. Barrier contacts have been fabricated by means of thermal deposition of Au in vacuum approximately 10^-6 mm Hg on the chemical etched surface of ZnS(Al) single crystals. Ohmic contacts where made of In+10%Cd-alloy. I-V, C-V and G-V plots have been measured. Spectrum and kinetic parameters of deep levels (DL) in the forbidden band were studied by means of modulation capacitance spectroscopy (MCS). X-irradiation causes the decrease of shallow donor traps concentration in near-surface region of ZnS and the decrease of surface state (SS) effective density N_SS in Au-ZnS contact. The radiation-stimulated changes in contact cannot be removed by the annealing. It has been stated that donor trap concentration and N_SS reaches the saturation at exposure doses higher, than 3 Cl/kg. Creation of any new DLs in ZnS forbidden band has not been observed within the limits of the exposure doses investigated. The changes of the DL kinetic parameters and their profiles after irradiation can be explained by the radiation-stimulated decrease of N_SS.

This paper surveys materials, design concepts, and applications for electrochromic devices. Specific discussions are given on the electronic structure and optical properties of crystalline WO₃, and of the Li+ dynamics in heavily disordered TiO₂.

Electrical transfer and diffusion of ions and the irreversibility of ion and electron processes in heterojunctions are responsible for degradation of ionic devices. These processes for electrochromic devices (ECD) determine the cycling capacity and lifetime. The basic problem here is how to match the electrochemical parameters (including chemical potential) of heterojunction. The experiments had been carried out on ECD based on system: (phi) -<ITO/WO₃//AAH//IrO₂/ITO>-(phi) , where AAH is solid electrolyte based on antimony acid hydrates. The cycling capacity and degradation processes of ECD are investigated by electro-optical and electro-chemical spectroscopy. The analysis of experimental data are based on assumption that electrode reactions changed composition of electrode and electrolyte materials and surface layers as well as constitution of heterojunction's interface. The conclusions of these investigations and problem analyses are some considerations about electrochemical battery model and cycling capacity of ECD. That depends on reversibility of solid state reactions on the electrode and ion insertion processes and phase stability of electrode and electrolyte materials. The ions of sublattices of immobile ions of solid phases and other components of these phases have to be stable against chemical interactions, diffusion and transfer of mobile ion during cycling.

We present in-situ x-ray absorption fine structure (XAFS) (at the W L₃-edge) and x-ray diffraction (XRD) studies of hydrogen intercalation into stable monoclinic (m-WO₃) and metastable hexagonal (h-WO₃) and cubic (c-WO₃) phases of tungsten oxide. The analysis of XAFS and XRD data allowed us to reconstruct the local environment around tungsten ions in the first coordination shell. The obtained results are compared with the existing structural models.

X-ray absorption spectroscopy (XAS) was used to study the local environment around tungsten and molybdenum ions in BaO-P₂O₅-WO₃ and CaO-P₂O₅-MoO₃ glasses having different composition of WO₃ and MoO₃ oxides. The W L_1,3 and Mo K edges x-ray absorption spectra were measured in transmission mode at room temperature using the synchrotron radiation emitted by the ADONE and LURE DCI storage rings, respectively. The analysis of x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) in glasses was performed in comparison with the results for a number of crystalline WO₃, CaWO₄, Na_0.66WO₃ alpha- MoO₃, beta-MoO₃ and amorphous a-WO₃, a-MoO₃ compounds. The results of the EXAFS modeling by two different methods [(1) multi-shell best-fit procedure within harmonic approximation and (2) model-independent radial distribution function approach] allowed us to extract detailed structural information on the first coordination shell of metal (W or Mo) ions. Using the obtained data together with the information given by XRD, EPR and optical spectroscopies, we propose the model of incorporation of W and Mo ions within the glass network.

The fundamental absorption edge of amorphous, polycrystalline and crystalline tungsten trioxide (WO₃) thin films obtained by different techniques (thermal evaporation, rf plasma sputtering, chemical gas transport) was investigated. Special attention was paid to correct measurements of absorption values of all WO₃ thin films taking into account the scattered light, interference effects and reflection losses. The indirect edge at 2.70 eV was determined for crystalline WO₃, but for crystal WO₃:Ti the direct edge in the same place (2.72 eV) was found. For polycrystalline WO₃ thin film first edge transition located at 2.76 eV had a quadratic dependence similar to the amorphous film at a higher photon energy (3.26 eV). Localized states are involved in these transitions with quadratic dependence. The gap energy shift from crystalline to amorphous WO₃ is explained by changes in the first coordination sphere of octahedral WO₃ cluster. Higher direct allowed transition at 4.1 eV is estimated both for amorphous and polycrystalline thin WO₃ films.

It is determined that vibrations of linear chains -O-W-O-W- in tungsten-oxygen network are rather independent. The value of vibrational frequency is determined by asymmetry of O equals W - O bonds.

Photochromism in V₂O₅ evaporated thin films has been investigated, especially with regard to its enhancement by adsorption of dimethylformamide (DMFA) molecules on the oxide surface. Measurements of the film optical properties in a wide energy range have been carried out giving a possibility to propose a model of the mechanism of the photochromic effect in the V₂O₅ films. At first, hydrogen atoms are detached from the adsorbed molecules of DMFA under light irradiation. They are predominantly localized near terminal oxygen atoms forming hydrogen bonds between hydrogen atoms and unshared electron pairs of the terminal oxygen atoms. Afterwards, under the action of light, some of these hydrogen atoms react chemically with oxygen atoms giving rise to the formation of oxygen vacancies. The 'blue' shift of the fundamental absorption edge is caused by two factors: (1) localization of hydrogen atoms near terminal oxygen atoms and (2) formation of oxygen vacancies due to breaking of V equals O bonds.

The changes that the electrochemical insertion of ions (M equals H, Li or Na) cause in the optical and mechanical properties of electrochromic tungsten bronzes, M_xWO₃, are reported. The commonly accepted assumption that the electrons and cations have separate effects, namely on the optical properties and film volume (stress), respectively, does not properly describe the results that are obtained with the three different cations. Differences between the cations are explained in terms of cation diffusion in a solid medium. Particular attention is given to the use of the laser beam deflection method, in conjunction with in- situ optical measurements, to characterize electrochromic thin films.

This paper deals with the influence of near-surface region on electrochromic properties of sodium tungsten bronze (STB) crystals. The surface element analysis of STB was carried out by SIMS and ESCA methods. Effects of anodic polarization and electrochromic coloration-bleaching on the near-surface of crystals were investigated. It was found that anodic polarization resulted to extraction of sodium from near- surface region. This process is responsible for the appearance of uninterrupted channels which are permeable to hydrogen ions. Their mobility defines sensitivity of electrochromic structure based on STB crystal. Mechanisms of anodic polarization and electrochromic bleaching-coloration of Na_xWO₃ are discussed.

For the first time photo-initiated injection of hydrogen was carried out into Ag- and Cu-halides (AgCl, AgJ, Ag₄RbI₅, CuCl) -- the materials which are very important for investigations of the photographic process. To carry out the photoinjection of hydrogen into the halides a double-layer structure was used. Onto a quartz substrate two thin films were evaporated one after the other: the first one -- a silver or copper halide film, and the second one -- an amorphous WO₃ thin film. The film double-layer structure was illuminated by UV-light from the side of the WO₃ film. The role of a hydrogen source was played by specially selected organic molecules previously adsorbed on the WO₃ surface. Hydrogen atoms detached from the adsorbed molecules under light illumination, diffused first into the WO₃ film and then, afterwards, migrated into the halide layer. Hence, illumination of the halide surface was accompanied by injection of hydrogen atoms released from the organic molecules adsorbed on the WO₃ surface.

Films of Me-Ce oxide (Me: Ti, Zr, Sn, W) and of Ni-Ce hydroxide were produced by reactive magnetron co-sputtering. Li intercalation in Me-Ce oxide, and H exchange in Ni-Ce hydroxide, were accomplished electrochemically. Electrochromism was quenched in proportion with the Ce content in Me-Ce oxide. Films of Zr-Ce (and to some extent Ti-Ce) oxide were able to serve as fully transparent counter electrodes, of much interest for transparent electrochromic devices. In Ni-Ce hydroxide, the Ce addition enhanced the capacity for charge exchange.

This report concerns a composite proton electrolyte suitable for use in electrochromic devices. The electrolyte consists of nanosize hydrated oxide (aluminum, silicon or antimonic) particles suspended in a poly(vinyl acetate) matrix. All of the water was strongly bonded, thus making the electrolytes less harmful without considerably decreasing the conductivity. The proton conductivity of the electrolyte was approximately 10^-4 S/cm at room temperature, practically independent of its amount of absorbed water.

The influence of exposure in vacuum of 10^-2 - 10^-3 Pa and temperature treatment at 720 - 730 K in water vapor atmosphere on stability of tungsten oxide films in 0.1 N H₂SO₄ electrolyte were studied. The processes that take place during the film exposure in vacuum, determine the reduction of charge injection at the constant voltage change condition. In the case of temperature treatment the opposite changes of charge injection were observed. This indicates to opposite processes in films during both expositions. According to exposures characters, they could be a reduction of tungsten oxide initiated by oxygen evacuation from film in vacuum and film oxidation in water vapor media at high temperature. The other processes during exposure time in vacuum, high temperature and electrolyte, are discussed.

Two batches of the samples of electrochromic cell with WO₃ and IrO_x electrodes and Sb₂O₅ (DOT) water based solid electrolyte were tested at constant contrast ratio up to 10⁷ cycles or stored during five years and the changes of current-voltage characteristics were studied. Two kinds of the changes were observed. The shift of curves along the voltage axis is supposed to be associated with the changes in the oxidation degree of tungsten oxide, while the changes in their shapes are associated with changes of water content in pores. The processes in the samples during cycling and storing are discussed.

The extended x-ray fluorescence fine structure (EXFLUFS) above the Ni and Cu K-edge of Ni, Cu, NiCu and NiO using the appearance potential regime by fast electron excitation was measured by means of scanning electron microscope with Si (Li) crystal detector and multichannel analyzer in the raster or single mode. The conventional extended x-ray absorption fine structure (EXAFS) type analysis was made in order to obtain the structural information. The Fourier filtered peak fitting with the phase shift correction from Teo & Lee gives the interatomic distances, which agree well with crystallographic and EXAFS data. The fitting results of experimental data suggest that conventional EXAFS phase shift correction can be safely used for EXFLUFS analysis with a little correction, if needed. The intensities of EXFLUFS peaks differ from that of EXAFS case, probably, because of non-dipole excitation, as well as the elastic scattering of primary electron before and after the inelastic scattering event. The EXFLUFS method is a bulk sensitive method which ensures several orders higher spatial resolution than in the synchrotron x-ray radiation case, as well as allows the deep core excitation in the wide energy range.

Photo- and radiation-induced destruction-polymerization transformations in amorphous As₂S₃ associated with coordination defects formation processes have been studied by differential IR Fourier spectroscopy method in the 400 - 100 cm^-1 region. All topological variants of these processes, statistically possible in the investigated samples, have been taken into account for physical consideration of the real structural transformations.

The dependences of linear losses coefficient alpha and two- photon absorption constant beta on structure and concentration x or average coordination number r changes of Ge-As-S glasses along the As-GeS₂, As-Ge₂S₃, As₂S₃-GeS₂ and As₂S₃-Ge₂S₃ section have been experimentally studied. The critical values of x and r at which the alpha and beta reach their extrema were determined. The obtained results have been discussed in terms of phase and structure-topological transitions.

The relaxation of optical, mechanical and chemical properties of as-evaporated amorphous As-S and As-Se films while storing them at room temperature is investigated. The As_xS_1-x films with arsenic content 0.3 less than x less than 0.4 are found to undergo maximal changes. It is shown that the phenomenon of dark self-enhancement of holograms (an increase of diffraction efficiency over time without any special treatment) can be used as an efficient method for investigation of relaxation processes in the amorphous chalcogenide films. The changes of diffraction efficiency in amorphous As₂S₃ films have been measured as a function of aging time and recording light intensity. The relaxation processes can be described by stretched exponential function often called as the Kohlraush-Williams-Watts function K(t) equals K₀ exp [-(t/(tau) _r)ⁿ] where (tau) _r is relaxation time of the process, n - a parameter, characterizing the relaxation process. It is assumed that the reason for the relaxation processes lies in internal mechanical stresses arising in the films during their preparation. A mechanism based on the photo-induced stress relaxation and viscous flow of amorphous semiconductor has been discussed.

Photoinduced structural changes in near-surface layers of amorphous As-Se and As-S films have been investigated using the microhardness method. Microhardness via indentation depth data for as-deposited, illuminated and aged in ambient atmosphere films is presented. The results obtained show that photoinduced increase in microhardness of surface layers up to approximately 1 - 1.5 micrometer are more pronounced in comparison with deeper layers. Increase in microhardness of the investigated films under exposure to atmosphere was also observed. Atmosphere-induced effect was more pronounced in the case of As-S films. Photo- and atmosphere-induced effects in the near-surface layers were found to be competitive. As a result, increase of the photoinduced effect in the microhardness of As-Se films and its decrease in the case of As-S films with decreasing indentation depth was observed. It was found that thermal stability of photo- and atmosphere-induced structural changes in near-surface layers are higher compared to volume ones.

The holographic sight development started as a search for a sight with improved accuracy, reduced size and greater simplicity. The main component of the sight is a hologram that generates an image of the reticle. This image can appear at any selected distance from the hologram, and can be located either in a plane or in three-dimensional space. The sight accuracy is that of the optics used in forming the hologram, which can be of excellent quality as only one set is needed for hologram recording. The field of view is unrestricted and a 'light-line,' an image of a line in space that extends from the sight to the reticle, guides the observer's eyes to the reticle. Sight designs are reviewed and designs described as the design evolved from a large 20 by 25 cm sight to the current compact sight for small arms. The latest design incorporates a laser diode light source and a pair of holographic elements to make the sight achromatic thus avoiding sighting errors due to laser diode wavelength drift.

The present state of the real time holographic recording in amorphous semiconductor films is reviewed including mechanisms, parameters, properties and applications. Effects of the coherent, incoherent and relaxational self- enhancement as well as the influence of the film structure relaxation are considered. Quasi-permanent sub-band-gap light holographic recording is reported for the first time. 157

Intrinsic properties of biological materials making them outstanding candidates for technical applications are briefly summarized in the paper. The origin of the light- driven optical non-linearity of bacteriorhodopsin (BR) is demonstrated. The fields of the most effective application of BR are analyzed on the basis of the last year's scientific publications. Attention is attracted to adaptive measuring interferometers with dynamic holographic beamscouplers based on BR. Several examples of such interferometers are discussed introducing one of the most promising BR application.

Kinetics of dynamic holographic gratings recording and erasure under spatial modulation of excitation (B-type) and relaxation (M-type) velocity of a reversible saturating media with immobilized bacteriorhodopsin is experimentally and theoretically studied. It is shown that the medium saturation cause non-exponential and non-monotonous behavior of holographic processes depending on the initial conditions.

Possibilities of optimization of the characteristics of light diffraction on holographic gratings and two-wave mixing in a cubic gyrotropic photorefractive piezocrystal with the help of choice of crystal orientation and polarization of light waves are investigated. It is shown, that dependences of optimum azimuth (Psi) ₀^max of light waves polarization, at which maxima of diffraction efficiency (eta) ^max and effective gain (gamma) ^max are reached, on orientation angle (theta) differ on 90 degree in area 90 degree less than or equal to (theta) less than or equal to 270 degree and practically coincide in other cases.

The effect of holographic grating (HG) size on their diffraction efficiency (DE) at different spatial frequencies is experimentally studied in amorphous AS-S-Se films. The HG size was changed by focusing the recording beams. It is found that reduction of the size from 1100 micrometer to 150 micrometer increases the maximal DE from 0.9% to 1.8%. Further reduction down to 20 micrometer decreases the maximal DE down to 0.08%. DE at lower spatial frequencies is attenuated more than at higher ones. The observed effects are explained by the nonuniformity of thin HG recorded by Gaussian beams as well as by the curvature of the focused wavefronts and peculiarities of the recording mechanism in As-S-Se films. It is concluded that minimization of hologram size in AS-S-Se films is feasible only down to 150 micrometers.

The latest advances in the field of holographic gratings and spectral devices is in calculation, manufacture and use of these gratings for spectral devices. The general theory of diffraction grating was developed in 1974. Although this theory is in wide use, not all the problems associated with the theory have been resolved. Theoretical calculations show that this is possible using a more complicated mounting of recording the grating. For recording of the grating with the compensation of the four aberrations it is necessary to use beams from opposite sides of the blanks. To examine this method special mathematical model was found. It is based on the ray tracing calculation, but includes two steps recording and the refraction in the glass blank. In this work we represent a system of nonhomocentric recording, which doesn't include aspheric or refractive optics, mathematical model of this system, spectral devices, which can be produced with the gratings, recorded in our system and the results of the mathematical model experiments with concrete examples of those devices.

The two-step persistent spectral hole burning (PSHB) of a hole in the inhomogeneous distribution function (IDF) of the optical transition frequencies in a three-level system by two successive light pulses, in the case of an exponentially increasing and decreasing first coherent pulse and an infinitely short second pulse is calculated. The compensation effect of the natural linewidth of the first excited level and the parameter describing the exponential decrease of the intensity of the first burning pulse is shown. The time-dependent zero-phonon line (ZPL) in luminescence spectrum in the recording scheme containing the time gate in front of the spectrometer with high resolution in the case of exponential opening and closing of the time gate is calculated. The effect of the compensation of the natural linewidth of the excited level and the parameter describing the exponential increase of the transparency of the time gate is shown.