We present a new class of single-photon devices for counting of both visible and infrared photons. Our superconducting single-photon detectors (SSPDs) are characterized by the intrinsic quantum efficiency (QE) reaching up to 100%, above 10 GHz counting rate, and negligible dark counts. The detection mechanism is based on the photon-induced hotspot formation and subsequent appearance of a transient resistive barrier across an ultrathin and submicron-wide superconducting stripe. The devices are fabricated from 3.5-nm-thick NbN films and operate at 4.2 K, well below the NbN superconducting transition temperature. Various continuous and pulsed laser sources in the wavelength range from 0.4 μm up to >3 μm were implemented in our experiments, enabling us to determine the detector QE in the photon-counting mode, response time, and jitter. For our best 3.5-nm-thick, 10×10 μm²-area devices, QE was found to reach almost 100% for any wavelength shorter than about 800 nm. For longer-wavelength (infrared) radiation, QE decreased exponentially with the photon wavelength increase. Time-resolved measurements of our SSPDs showed that the system-limited detector response pulse width was below 150 ps. The system jitter was measured to be 35 ps. In terms of the counting rate, jitter, and dark counts, the NbN SSPDs significantly outperform their semiconductor counterparts. Already identifeid and implemented applications of our devices range from noninvasive testing of semiconductor VLSI circuits to free-space quantum communications and quantum cryptography.

We analyze theoretically the modal dispersion of N-period planar waveguides with a bilayer unit cell containing thin magnetized metal film. Three basic configurations of external dc magnetic field are discussed: transversal, polar, and longitudinal. On the basis of coordinate-free surface-impedance formalism we derive compact analytical formula for the characteristic transmission matrix of the magnetized layer in case of polar configuration, which is to our knowledge the novel and non-trivial result. We show that increasing the number of periods leads to prohibition of qTE mode guidance, but find it unrealistic to tailor the band structure of the system by magnetizing the metal films. Alternatively, we propose to control polarization states of the guided modes through magnetization.

We report developments in lanthanum doped PbZrO3:PbTiO₃ solid solution (PLZT) based electrooptic switches for a new class of spatio-temporal modulated lasers. The contents includes a user's adapted approach to the electrooptic properties of PLZT, propagating and scattering of the electromagnetic radiation, and the impact of electrodes, its design, and deposition, housing on thermally conducting substrates, and antireflection coatings. Performance specification is presented as a compromise between the thickness of PLZT plate minimized by scattering considerations, and the shape and distance of electrodes sufficient for the driving voltage and diffraction restrictions. Another set of specifications comprises the energy dissipation growing at shortening the pulses of driving voltage and at increasing the switching frequency as well as electromechanical effects exhibiting itself in a difference between the static and pulsed voltage retardation and coupled optoacoustic oscillations. A balance between these factors is provided by thin (300-700μm) PLZT plates and by driving fields not exceeding 10⁶V/m with embedded electrodes spaced at about 500 μm⁵.

We report advancements in electrically controlled scanning of the direction of laser radiation preceded in 1-3 with application to the YAG:Nd and Cu vapor lasers its key specifications determined by intracavity PLZT spatio-temporal light modulator (STLM) located within a linear conjugate cavity. In the present work the results of an experimental research into the radiation characteristics of the laser with a polarizing output of radiation from the resonator are given. One of the lenses of the conjugate laser resonator is a cylindrical lens. Due to optical relief of the STLM and use of a cylindrical lens the output energy of a lasing pulse is increased signifciantly. The laser radiation scans along the vertical coordinate and is specified by packets of 10-20 pulses with the 15-50 kHz repetition frequency in a packet, up to 10 mJ energy, and the 150-250 ns pulse duration. The laser is operating in the 5-10Hz pulse repetition regime with 1 millisecond duration pumping pulse. Movement of the article during marking provides the second coordiate. STLM based scanning laser is an effective alternative both to jet markers for articles moving on a conveyor belt and the existing laser markers with optomechanical scanning. Capabilities to enhance overall performance of the scanning laser are discussed and samples of markings obtained on different materials demonstrated.

The work is devoted to investigations of physical and chemical processes taking place at the boundary between a thin gold film subjected to low-temperature annealing and gas or liquid media. Besides, the work is aimed to research formation of protective, stabilizing and orienting ones in optimization of characteristics inherent to biochemical sensors based on the effect of optical excitation of the surface electromagnetic wave in the thin gold film as well as in investigations of the reflection angular function when using the mode of attenuated internal total reflection. Shown is the necessity to apply the procedure of 120°C temperature annealing that can result in smoothing a small-scale relief of the gold surface and obtaining some optimal parameters of a resonance curve as well as in formation of defectless protective and stabilizing nano-dimensional layers. To protect gold surface, studied are several mechanisms of layer formation in the cases of gold thiolate and gold sulfide. The way of oriented fixation of a sensitive molecular layer using the non-organic cooper aminopentacyanoferrate layer is worked out.

Two prototype models of pressure sensors using side-scattering optic fiber as the sensitive element have been designed and experimentally assessed. The study showed that the use of 600-micron silica core side-scattering fiber resulted in 5 to 6 times higher sensitivity compared to the oridinary PCS fibers.

Investigations on the laser-induced reduction of advanced ceramic materials, including high-temperature supercondcutive (HTSC) ceramics, are presented. Here the oxygen content of the material is locally decreased by CW YAG:Nd laser irradiation in H₂ atmosphere. Direct laser-written metallic stripes into the weakly conducting sample surface had been tested by standard 4-point-probe technique in He dewar. New data about resistance temperature dependences of 100% laser reduce dstripes of HTSC Y-Ba-Cu-O ceramics has been determined. Our experimental data are in good agreement with Matthiasen's law with respect ot laser-written electrodes as YCu₃ alloys. As for high resistive stripes in HTSC ceramics begin written into the surface under imcomplete reduction regime we have found similar resistance behavior to random network of Cu fine particles connected 2D through thin oxide barriers. In the case of Bi-based HTSC ceramics a controversial picture takes place - low melting temperature of Bi oxide gives rise to segregation of Bi microspheres along the stripes corresponding to incomplete electroding. Although the laser-assisted surface alloying and metallization of bioceramics has been performed.

This paper studies the correlation between the time-of-flight (TOF) of laser pulses and paper density, basis weight, thickness and the beating of pulp. Paper samples made from unbeaten and beaten pulp were compressed from 500kg/m³ to 1100kg/m³ and laser pulses were shot through them during pressing. Changes were observed in the thickness of the samples and in the TOF of the laser pulses. The results show that TOF decreases during comrpession. This indicates that distances between the various scattering surfaces decrease. This phenomenon becomes more pronounced as the basis weight increases. The beating of the pulp before papermaking increases the number of scattering surfaces, thus broadening the laser pulse and causing delay. These two effects cannot be separated with the equipment used. Papers made from different pulp types each have unique delay constants.

AlN-Y₂O₃ ceramics is studied as a material for application in the area of ultraviolet radiation (UVR) dosimetry. The properties of optically stimulated luminescence (OSL) and thermally stimulated luminescence (TL) revealed by AlN ceramics are characterized and considered for practical application. A special attention is devoted to studies of the spectral properties of the material, including stimulated luminescence. Spectral properties of the material make it potentially suitable for dosimetric application both in UV-C region (200-290 nm), where it has the maximum sensitivity, and in UV-B+UV-A (290-350 nm) region, where the spectral behavior of its sensitivity coincides rather well with that of the human skin.

High-frequency electrodeless light sources (HF EDLS) are widely used as bright radiators of narrow and intensive atomic and ionic spectral lines, covering the spectrum from VUV to IR. Main characteristics of HF EDLS are high emitted spectral line intensity, long service life, and in general, narrow spectral line shapes because of low-pressure of filling elements. In this work we give a short overview of the use of HF EDLS, containing Hg, Te, Se, Zn, Pb, As, Sb, Bi, Tl, In, Cd, Sn, in Zeeman Atomic absorption devices for assaying natural, drinking, waste and technical water as well as air, soil, food products and biological samples. The first steps are made for optimization of Ge, Ga, P, S, Ag, Cu HF EDLS. Enhanced detection limits are obtained in comparison with hollow cathode lamps.

For the first time previously developed iodine resonance spectra source has been tested in flash photolysis experiment. Quantitative measurements of concentration kinetics of iodine atomic species in a I₂+O₃ system are possible. The 183.038 nm resonance absorption transition of I(²P_3/2) in previously developed EDL has been studied; dependence of self-absorption and self-reversal on iodine partial pressure in the discharge volume has been measured. The search for optimal conditions for an iodine EDL with minimized self-absorption and sufficient intensity were made. In condition of flash photolysis with previously described method it is possible to determine the emission temperature, oscillator strength and corresponding absorption cross section for the I(²P_3/2) transition at 183.038 nm. With special set-up shown here it is possible to use the continuous light sources for absorption spectroscopy of molecular iodine species together with atomic iodine line soruce for resonance absorption spectroscopy of atomic iodine sepcies. There are evidences that bromine sources could be used in similar ways.

We report on fabrication and ultrafast photoresponse of novel, freestanding low-temperature-grown GaAs (LT-GaAs) photoconductive (PC) devices. 1-μm-thick, LT-GaAs single-crystal films were grown by molecular beam epitaxy at the temperature range of 200°C to 250°C. Next, the films were patterned to the desired device sizes, lifted-off from their host substrates, and placed on predetermiend places on either SiO₂/Si or MgO wafers. Our freestnding LT-GaAs devices consisted of either approximately 20-μm by 20-μm PC switches, or 150-μm by 150-μm metal-semiconductor-metal (MSM) interdigitated structures with Ti/Au fingers patterned directly on top of the LT-GaAs film. For testing purposes, our devices were integrated with Ti/Au coplanar striplines, fabricated directly on SiO₂/Si and MgO substrates. The test structures were illuminated with 100-fs-wide optical pulses and their time-resolved photoresponse was measured with an electro-optic sampling system, characterized by 200-fs time resolution and sub-millivolt sensitivity. Using 810-nm optical excitation, we recorded as narrow as 360-fs-wide electrical signals (1.25 THz, 3-dB bandwidth) for PC switches, resulting in 155 fs carrier lifetime in our freestanding LT-GaAs. For both types of devices, the photoresponse amplitude was a linear function of the applied voltage bias, as well as a linear function of the laser excitation power, below well-defined saturation thresholds. Our freestanding photo-switches are robust and very reproducible. They are best suited for applications in hybrid optoelectronic and ultrafast electronic systems, since they can be placed at virtually any point on a test circuit.

Recently efficient room temperature lasing material for this IR range has been demonstrated in II-VI semiconductors doped with transition metals. These dopants incorporated into CdSe substitute metallic atoms and create deep levels in the band gap. The room temperature mid-infrared absorption in CdSe:Cr is observed due to the intracenter transtion ⁵T₂→⁵E of Cr²⁺ ions. These tetrahedrally-coordinated ions are especially attractive as laser centers on account of high luminescence quantum yields for emission in the 2-3 μm range. Electrical and optical measurements are obtained with CdSe single crystals doped with chromium from a gas soruce CrSe over a wide temperature range (500-1050°C). These processes are intended to control the concentrations of the impurity and intrinsic defects. The low temperature annealing of CdSe crystals in CrSe atmosphere allows obtaining high electron mobility up to 9000 cm²/Vs at 80 K and dmeonstrates the low native defect concentration. A high temperature annealing gives a rise of electron concentration with decreased mobility. Optical absorption measurements show that at the high annealing temperature effective doping with Cr takes place. The impurity absorption beyond the absorption edge is interpreted by the excitation of Cr²⁺ and Cr¹⁺ deep levels. Mid-infrared absorptin spectrum in 1.2-3.8 μm was measured. A discovered absorption peak at 1.9 μm corresponds to the intracenter transition ⁵T₂→⁵E of Cr²⁺ ions. The intensity of this peak increases with increasing annealing temperature due to the growth of the impurity concentration. The maximal absorption coefficient in peak has a value of 4 cm^-1 Cr²⁺ concentration in samples was calculated by using the peak absorption coefficient and it was varied from 10¹⁷ to 2×10¹⁸ cm^-3.

A detailed study of both the optical and electrical low-frequency noise and correlation factor between optical and electrical fluctuation characteristics of single-mode multiple quantum wells (MQW) curied-heterostructure (BH) distributed feedback (DFB) laser diodes has been carried out under a wide current range. These techniques have been used to assess the structural differences between devices that exhibit superior and poor performance and reliability. It has been concluded that for the devices investigated here, the poor device performance characterstics (larger threshold current) and poor reliability are induced by the existence of defects in the interface between the active region and burying laser. These defects generate leakage currents that lead to teh larger threshold current. Defects migration during ageing forms clusters, and this leads to the poor reliability of the lasers. We demonstrate that the low-frequency noise investigations can detect the presence of defects that induce short device lifetime.

Thermal lens measurements on the thin films of ferrofluid located between the transparent indium-thin oxide (ITO) electrodes on glass substrate has been performed. In the presence of axial electric voltage we have observed suppression of characteristic far field patterns (rings) of thermal lens replaced by moving labyrinth structures. Critical value of the suppression field, for example in kerosene based ferrofluids - 13 kV/cm, and for ionic ferrofluids - 2,5 kV/cm, has been estimated.

Elementary hologram (holographic grating) recording and their coherent optical erasure have been experimentally studied in azobenzene oligomer (ABO) layers differing by their chemical composition, matrices and by the connection type of azobenzene chromophores to the matrix (dispersed or covalently bound). The best holographic parameters (7.9% diffraction efficiency and 86 J/cm² specific recording energy) were achieved in the samples with covalent bonding to the matrix. Vector recording is also possible. Recording is unstable and reversible. The coherent optical erasure studies have shown its efficiency dependencies on the initial diffraction efficiency, erasing beam intensity and grating period which are different for three groups of ABO samples. The conclusion is made that recording is due to the photoinduced alignment of the azobenzene chromophores followed by refractive index changes. These are the first results and further studies are in progress.

A detailed study of the amorphous As-S-Se and As₂S₃ films as recording media for optical holography and electron beam lithography is presented. The results on R&D of resist based on the amorphous As-S-Se thin films for manufacturing of embossed holographic labels are discussed. The holographic recording of transmission and Bragg gratings was studied.

Organic-inorganic films based on SiO₂, containing Disperse Red 1 (DR1), carbazole units and 2,4,7-trinitro-9-fluorenone (TNF), have been prepared by a sol-gel technique. Diffraction gratings have been produced through different effects: photoinduced birefringence and photorefractivity, using 488.0 nm and 632.8 nm light, respectively. Pure polarization holographic birefringence gratings have been investigated and diffraction efficiencies higher than those obtained by light intensity modulation have been measured. The study of the temporal behavior of the diffraction efficiencies makes possible the identification of different processes involved in the DR1 molecular orientation: angular hole burning (AHB), angular redistribution (AR), Cis molecules gain has been determined by two-beam coupling (2BC) measurements. The effect of the polarization of the writing beams on the grating and of a circularly polarized photoisomerizing radiation during grating erasure has been interpreted in terms of an orientation contribution to the grating formation.

The amorphous As₄₀S₁₅Se₄₅ films as recording media for optical holography were studied. The results on research of transmission and Bragg grating holographic recording and readout conditions are presented. The recording of transmission holographic gratings was performed by He-Ne (0.6328 μm) or Kr⁺ (0.6764 μm) laser beam, while the readout of the diffraction efficiency was made at Bragg angle using He-Ne (0.6328 and 1.15 μm) or diode (0.805 μm) laser lines. It is shown that self-enhancement of Bragg grating reflectors is possible. The influence of thin film interference conditions on holographic recording parameters is demonstrated.

Diffraction anisotropy (DA) defined as the polarization dependence of the amplitudes (amplitude DA) and phases (phase DA) of the diffracted light waves is studied in the case of a sinusoidal transmission amplitude-phase grating both theoretically and experimentally. Theoretical analysis was mainly based on the Kogelnik's coupled wave theory (KCWT) and also on the conclusions of rigorous coupled wave theory (RCWT) and effective medium theory (EMT). Experimentally gratings with 0.42 μm period in a-As-S-Se films at 632.8 nm were studied. KCWT predictions were compared with those of RCWT and EMT as well as with the experimental DA results. It is found that KCWT properly describes the first order amplitude DA, and more roughly also the zeroth order amplitude DA. The zeroth order phase DA is wrongly described by KCWT. It is also found that polarization dependent Fresnel reflection effect is much stronger than DA therefore p-polarized hologram recording is preferable.

The relief-phase holographic gratings in amorphous As-S-Se thin films were recorded and studied. The holographic recording was performed by He-Ne laser (0.6328 μm). The influence of etching and cohernet self-enhancement processes on the formation of surface relief in amorphous As-S-Se thin films was studied.

We propose a bidirectional multi-channel cross-connector for two-way optical communications with array of the photorefracttinve crystal. The communication channels are connected bidirectionally by double phase conjugation in each photorefractive crystal. The wiring pattern is possible to determine by the beam that controls whether it generates the double phase conjugation in the crystal. This all-optical switching is effective method to solve the problems of the electrical wiring techniques such as the electro-magnetic interference and the thermal generation. We analyze the connection efficiency for coupling strength of the two four-wave mixing interaction region in the double phase conjugation and investigate teh intensity of control beams for sufficiently switching. We also experiment on the bidirectional connection switch and estimate the connection efficiency and the transmission efficiency.

In this report, we propose a photorefractive (PR) nondestructive memory with a Kitty-type phase conjugate mirror (Kitty PCM). Nondestructive readout without any fixing technique and high quality image rewriting can be achieved in this memory. An optical feedback circuit including a Kitty PCM is added on to the usual PR memory in the nondestructive reading method. The nondestructive readout means that the recorded data of the dynamic hologram, generally erased by the exposure of the reading beam, is maintained by only all-optical configuration. The nondestructive readout in this memory is achieved by the hologram rewriting effect that is generated by the reillumination of the diffraction beam reflected by a phase conjugate mirror. But a conventional Cat-type self-pumped phase conjugate mirror (Cat SPPCM) has insufficient reflectivity to obtain large feedback rate required for this nondestructive readout. In this report, we calculate and experiment on the phase conjugate reflectivity and the time response property of the Kitty PCM and show it has the advantages of high reflectivity and fast response time. We perform the experiment on our rewritable PR memory using BaTiO₃ crystals and demonstrate the long time reading over 18 minutes is achieved in this memory.

We have proposed the all-optical fault-tolerant holographic memory (FTHM) that automatically restores the dropout data by the constant rewriting method. In this method, the constant rewriting is conducted in the normal state or dropout state, so this data restoring is inefficient in terms of the restoration speed and the energy consumption. In this paper, we propose a dynamic dropout data restoring technique inthe FTHM. In this dynamic technique, the strength of the rewriting effect change in proportion to dropout level, i.e. if dropout technique can improve the restoring speed and reduce the energy consumption for restoring. First, we analyze the temporal response of the output efficiency and the hologram. Next we analyze the dependency of the output efficiency on the coupling strength in the two crystals and the incident condition of two beams, and estimate the coupling strength threshold and the ratio of the incident beams in order to maintain the stored data. Finally we experiment on the dropout data restoring by using BaTiO₃ as photorefractive crystal, and achieve the data restoring for 2-3 seconds and the over 25 minutes readout.

We have proposed the all-optical interconnection, in which the photorefractive four wave mixing (FWM) is used as the core, by full-linear resonator (FR) with a beam splitter (BS) and a self-pumped phase conjugate mirror (CAT). The index grating of the FWM region inside the photorefractive crystal (PRC), which determines the connection pattern, was maintained by the rewriting effect of the input signal beam and the resonance beam between the CAT and the BS. But the power of the resonance beam was wasted by the optical reflection at the crystal surface of the CAT and the PRC. Therefore the rewriting effect of the connection pattern could not be obtianed sufficiently. In this report, we propose the integrated full-linear resonator (IFR), in which a self-pumped phase conjugation (SPPC) region and the FWM region are formed in one PRC, to solve this problem. Compared with the conventional FR, the power loss of the resonance beam by the optical reflection can be prevented and the resonance beam can be used efficiently for the maintenance of the connection pattern. We experiment on the 2×2 all-optical interconnection with the IFT by using BaTiO₃ crystals and Ar⁺ laser. It is shown that the maintenance time of the connection pattern can be extended sufficiently by using IFR.

We propose a new type of the fault tolerant all-optical router (FTAR) by using an all-optical switch with photorefractive two-wave mixing. FTAR can detect a cutoff of a main transmitting line and automatically reroute a signal beam from the main line to a backup line. These functions can increase communication reliability of optical wireless. FTAR is composed of ony all-optical devices without any electronic devices or any mechanical operations. In the new type of FTAR, the routing of the signal beam is controlled by a control beam transmitting on the main line from a different light source at a receiver in the opposite direction with the signal beam. Compared with the previous type of FTAR composed of two photorefractinve crystals, the new configuration offers the simplification of the construction and high transmission efficiency of the signal beam. In this report, we experiment on the FTAR by usign a BaTiO₃ and Ar⁺ laser whose wavelength is 514.5nm, and confirm the fundamental fucntin of FTAR. We give comparison of the result with the numerical analysis. We also analyze the dependence of the switching time on the input beam intensity of the crystal by a numerical analysis and an experiment.

Results of investigation of processes providing formation of hologram diffraction gratings based on As₂S₃ layers are represented. Using the method of atomic force microscopy the groove profile shape is studied for these gratings in dependency on exposure values. Carried out are measurements of their diffraction efficiency dependencies and analyzed is their relation to the relief shape of the grating surface.

Electrochromic films based on oxides of W, Ni, and Ir were made by reactive DC magnetron sputtering. Enhancements of the bleached-state transmittance, by adding Al or Mg to oxides of Ni or Ir, were documented. Sputtering of W oxide in the presence of hydrogen, and post-deposition treatment of Ni oxide in ozone, produced charge balancing of the components of the electrochromic device in a way that enabled facile assembly by lamination.

The performance is actual problem of electrochromic coatings. The service and shelf life and cycling capacity are main performance characteristics. By solid-state ionics point of view any electrochromic cell based on phenomena with ion insertion - extraction processes is functioning as solid-state rechargeable battery. The main performance characteristics of electrochromic cells are similar. Performance of electrochromic coatings based on amorphous WO₃ films and protons conducting electrolytes is limited by reversibility of ion insertion-extraction reactions, which causes degradation of cell components. The migration of water in the cell and hydration together with ion insertion-extraction reactions of the WO₃ film have main role in formation of new phases, which determine the value of cycling capacity. The cycling capacity at constnat coloration intensity is limited by initial total number of active tungsten ion sites for induced color centers at inner surface of porous WO₃ film. The more probable transformation of phases in hydrated WO₃ films during cycling, which can be related to loss of active tungsten ion sites, is transformation of octrahedral structural units of H_xWO₃nH₂O to tetrahedral H₂WO₄mH₂O.

Porous tungsten oxide films have been prepared by a nonhydrolitic sol-gel method using poly(ethylene glycol) (PEG) as a structure directing agent. The method entails the hydrolysis of an ethanolic solution of tungsten ethoxide (formed by the reaction of WCl₆ with ethanol) followed by condensation and polymerization at the PEG-tungsten oxide oligometers interface. A highly porous WO₃ framework was obtained after PEG was burned off by calcination at a relativley low temperature. AFM images of the films treated thermally show an ordered material rather than microscopic particulates. Both fibrilar nanostructures and striped phase can be obtained via this approach, depending on the concentration of PEG in the coating solution. XRD data from the fibrils indicate that they are crystalline with very small crystals, whereas the striped phases obtained with 20% PEG correspond to two crystalline phases, one, the stoichiometric WO₃ and the other one an oxygen deficient phase, containing larger crystals (~28 nm). The results show that PEG promotes the formation of oxygen deficient phases and delays crystallization. Compared to WO₃ with no PEG, the optical and electrochromic properties of the macroporous tungsten oxide films appear to be significantly improved. The formation of organized nanostructures is tentatively accounted for by the strong hydrogen bonding interactions between PEG and the tungsten oxide oligomers.

Structural investigations of the short range order around iridium and oxygen ions in nanocrystalline iridium oxide thin films, prepared by dc magnetron sputtering technique, were performed by x-ray absorption spectroscopy. The Ir L₃-edge extended x-ray absorption fine structure and the O K-edge x-ray absorption near edge structure signals were measured at room temperature and analyzed within ab initio multiple-scattering and full-multiple-scattering approaches, respectively. The x-ray absorption spectroscopy results indicate the presence in the films of orderd regions - nanocrystals, having a size of about 10 angstrom and a structure rather close to that in crystalline iridium oxide IrO₂. Such evidence agrees well with observations by x-ray diffraction, suggesting that the thin films are x-ray amorphous.

Indium tin oxide (ITO) is optically transparent semiconductor that finds extensive applications in liquid crystal displays, photovoltaic cells, touch screen displays, electrochromic smart windows and more. As with all such electrode materials, there is a compromise between conductivity and optical properties. Different substrate materials and underlying layers are playing important role in transparency (better contrast and less absorption, increased brightness), surface morphology (smoothness, homogeneously) and conductivity of the ITO films. We compared optical, electrical and morphology properties of ITO films onto polymer substrate, obtained from company "SIDRABE Inc." (Latvia) and ITO films onto glass substrate obtained by us.

We review novel group of fast infrared detectors based on hot carrier effects in nonuniform Ge, Si, GaAs, AlGaAs and Ti/n-Si Schottky structures. It is demonstrated that the devices can be used to detect infrared pulses of nanosecond duration at room temperature. Physcial mechanism responsible for the photovoltage signal formation both in p-n and l-h junction of moderately and degenerately doepd semiconductors are analyzed and discussed. The influence of aluminum arsenide mole fractin on th emagnitude of the photoresponse to infrared radiation in AlGaAs/GaAs p-n junction is studied. Operational principle of the Schottky barrier detector at various radaition frequencies is considered. It is shown that photoresponse of the Schottky barrier detector superlinearly depends on infrared radiation intensity.

Recent advances in the epitaxial growth of GaN and its alloys with Al and In have led to major improvements in the performance of short-wavelength visible and UV diode lasers and solar-blind detectors for UV wavelengths. A decrease in defect densities to less than 10⁶ cm^-2 by an epitaxial lateral overgrowth technique has enabled the fabrication of 405-nm InGaN lasers emitting 30 mW continuously with 15000-h lifetimes. Laser wavelength coverage has been extended to 366 nm in the UV. Initial results in the development of quantum dot lasers have been reported and active mode locking of 409-nm lasers has yielded 30-ps-long pulses, of interest for frequency upconversion. AlGaN photodiodes with a band-edge wavelength of 285 nm, appropriate for solar-blind detection, have been fabricated and low dark-current densites (10 nA/cm² at -5-V bias) have ben reported. Gains of 10 when operated in the linear mode and gains of ~10⁶ in Geiger-mode operation have been obtained in GaN avalanche photodiodes.

The study is addressed to the decay dynamics of Bloch oscillations in GaAs/Al_0.3Ga_0.7As superlattice as a function of temperature and excitation density - characteristics those are very important for an emitter design. It is demonstrated that in the both cases the coherence of the wave packets is mainly lost due to the interband dephasing of the system. It is shown that the intraband dephasing is nearly independent on temperature within 9K-80K; the increase of exictation densities up to 1.5 109 cm-2 has weak influence on the decay dynamics of the Bloch oscillations (the decay rate is found to be about 0.6 ps-1 within all studied range). Dc electric field driven Bloch emitter based on three terminal device containing semiconductor superlattice is suggested and discussed.

Our study is concerned with peculiarities of intense CO₂ laser light detection in narrow-gap semiconductor p-n junctions. Samples of InSb, PbTe and HgCdTe were udner investigation. We present experimental evidence of free carrier heating phenomenon in the semiconductors and its influence on photovoltaic signal. We show, that in particular cases, depending on laser light intensity and applied bias, the hot carrier photosignal of opposite polarity may predominate over the ordinary photovoltaic one.

Nanowires are expected to play an important role in future electronic, optical devices and nanoelectromechanical devices. Measuring the electrical and mechanical properties of nanowires is however a difficult task due to their small dimensions. Here we report the use of an in-situ microscopy technique, which combines transmission electron microscopy (TEM) with scanning probe microscopy (SPM), to investigate the electrical and mechanical properties of metallic and semiconductor nanowires. Additionally, in this paper we describe a novel approach for synthesizing mesoporous silicas with tunable pore diameters, wall thickness and pore spacings that can be used as tempates for the assembly of semiconductor nanowire arrays. Silicon and germanium nanowires, with size monodisperse diameters, can readily be formed within the mesoporous silica matrix using a supercritical fluid inclusion technique. These nano-composite materials display unique optical properties such as intense room temperature ultraviolet and visible photoluminense. The implication of these mesoporous nanowire materials for future electronic and opto-electronic devices is discussed.

Structural investigations of nanocrystalline iridium oxide thin films, prepared by dc magnetron sputtering technique were performed by scanning probe microscopy (SPM). SPM studies, using both atomic force microscopy (AFM) and scanning tunnelling microscopy (STM), indicate that the thin films are composed of grains with a size of about 20-50 nm. Fine crystallinity and small RMS microroughness of the films, being well below 2 nm, make iridium oxide thin films promising candidates for nanolithographic applications. The possibility to perform nanolithograhpic processes at a scale of less than 150 nm was successfully examined in AFM and STM modes.

New method for 3D nano-scale imaging was developed that combines a traditional scanning probe techniques with a local laser ablation processing of the surface of a sample. The technology opens new possibilities for ultra precise (down to atomic resolution) subsurface studies, whereas the traditional SPM sensitivity is limited to only few atomic layers. We demonstrate that our new experimental set-up can also be used for other investigations, e.g. in in situ characterization of surface processing. The approach is potentially interesting for many applications, like volume nano-imaging, in situ studies of a stimulated nano-assembling or growth, monitoring of laser processing and cleaning, etc.

Diffuse optical tomography is emerging as a viable new biomedical imaging modality. Using near-infrared light this technique probes absorption as well as scattering properties of biological tissues. First commercial instruments are now available that combined with appropriate image reconstruction scheme allow to obtain cross sectional views of various body parts. The main applications are currently brain, breast, limb and joint imaging. While the spatial resolution is limited compared to other imaging modalities such as MRI or X-ray tomography, diffuse optical tomography provides for a fast, inexpensive, acquisition of a variety of physiological parameters that are otherwise not accessible. We present here a brief overview over the current state-of-the-art technology and some of its main applications.

A novel approach to the problem of non-invasive diagnostics is presented, which relay son a combiend optical and chemical excitation of the tissue, by employing white light and topical application of acetic acid solution, respecitvley. Acetic acid-tissue interaction results in a transient alteration in the light scattering properties of the abnormal tissue selectivity. A specially developed Spectral Imaging system was used for the in vivo spectral imaging and analysis of the tissue and for the measurement, as a function of both time and location, of the acetic acid-induced alterations in the tissue scattering properties. Modeling and fitting of the experimental data result in the calculation of the kinetic constants of the marker-tissue interaction process, and spatil distribution of whcih is visualized with the aid of a pseudocolor scale. Clinical evaluation of both methodology and technology in normal, precancerous and cancerous lesions of cervix show that the measured kinetic data contain specific information, which enables the differentiation between cancerous and non-cancerous lesions, as well as between dysplasias of different grade. The calculated map of the kinetic constants provides information for the spatial distribution of the lesion's grades, thus enabling the detection of incipient lesions and the precise localization and classification of pathologic tissue areas.

To develop PDT beyond treatment of thin superficial tumors, to also be an efficient treatment alternative to deeply located and/or thick tumors, a system based on interstitial illumination using multiple fibers has been developed. Conditions that could benefit from such a treatment modality are for instance malignant brain tumors and tumors in the oral cavity. In interstitial PDT one needs to use multiple fibers for light delivery in order to allow treatments of tumors larger than a few millimeters in diameter. Our sytem consists of a laser light source, a beam-splitting system dividing the light into three or six output fibers and a custom-made dosimetry program. The concept is then to use these fibers not only for delivering the treatment light, but also to measure parameters of interest for the treatment outcome. The fluence rate of the light emitted by each fiber is measured at the positions of the other fiber tips. From these results the light dose at all positions could be recalculated. Changes in optical properties as well as bleaching and concentration of the photosensitizer during the treatment could be monitored and compensated for in the dosimetry. Tumors have been treated both in experimental studies and in patients with thick superficial Basal Cell Carcinomas. Almost all treated skin lesions responded with complete response.

A hand-held prototype device for detection and processing of the tissue-remitted optical signals has been developed and tested. The photoplethysmography (PPG) principle was applied to follow the dilation and contraction of skin blood vessels during the cardiac cycle. Cardiovascular condition of the monitored person was assessed by temporal analysis of the recorded PPG signals as well as by shape analysis of the mean single-period PPG signals.

We compared two different techniques for non-invasive registration of fingertip skin blood flow changes in 5 healthy volunteers during local arm heating in the water bath from 21°C to 42°C. The laser-Doppler flowmetry (LDF) probe was attached to the pulp of the index finger, while the thermal clearance (TC) probe was fixed to the pulp of the middle finger. Computer simulation method, provided by the MATLAB package, was introduced to speed up the frequency response of the TC probe. By correlation analysis we evaluated the similarity of LDF and TC recordings. The median correlation coefficient for the relationship LDF versus TC equaled 0.74, the range being from 0.63 to 0.82. After an introduction of the computer-based frequency correction, the correlation increased till 0.88 with the range from 0.82 to 0.91. The corresponding improvement in r² ("goodness to fit") was 41%.

Operation of the device is based on alternative generation of pictures for left and right eyes on the monitor screen. Controller gives pulses on LCG so that shutter for left or right eye opens synchronously with pictures. The device provides frequency of switching more than 100 Hz, and that is why the flickering is absent. Thus, a separate demonstration of images to the left eye or to the right one in turn is obtained for patients being unaware and creates the conditions of binocular perception clsoe to natural ones without any additional separation of vision fields. LC-cell transfer characteristic coodination with time parameters of monitor screen has enabled to improve stereo image quality. Complicated problem of computer stereo images with LC-glasses is so called 'ghosts' - noise images that come to blocked eye. We reduced its influence by adapting stereo images to phosphor and LC-cells characteristics. The device is intended for diagnostics and treatment of stabismus, amblyopia and other binocular and stereoscopic vision impairments, for cultivating, training and developing of stereoscopic vision, for measurements of horizontal and vertical phoria, phusion reserves, the stereovision acuity and some else, for fixing central scotoma borders, as well as suppression scotoma in strabismus too.

Studies are focused on design and appraisal of an objective test of the quality of stereovision depending on optical stimuli blurring and detecting of the stereovision threshold at various stimuli blur degree. The method is based on the principles of grayscale and color random dot stereotests. Experiments may be divided with respect to the principle of demonstration: 1) the blur is modeled by defocusing an optical lens - the strength of the optical system is varied at a constant quality of the stimulus, or 2) the blur is simulated on the computer screen - here the quality of the stimulus varies. To obtain an independent description and to measure blurring the experimentally demonstrated images are analyzed with regard to modulation depth, Fourier frequencies and by cross-correlation.

Studies are focused on design and appraisal of an objective test for assessment of the stereovision quality in unfavorable conditions. Stereostimuli of different colors are used while the contrast of one of the stimulus being varied. Tests are based on principles of black-and-white and two primary color random dot stereotests. Experiments are divided by the method of stimuli display and separation: 1) stereoeffect is obtained haploscopically - by use of spectacles with color filters (blue and red) or prisms, 2) stimuli separation is obtained by liquid crystal shutters when both eye stimuli are demonstrated with a different delay. The stereovision threshold is determiend at different stimuli disparities simulating the random dot stereotests on a computer monitor with a variable contrasts of one-color stimuli. The applied test differ by stimuli geometry, separation of vision channels, and by data processing. Tests have been appraised and may be used in stereovision studies.

Colored filters have been used as possible aids for perception in case of congenital color vision abnormalities. Higher stimulation for L cones in one eye (red filter) and for M cones (green) in other eye acts as a simple method to interfere in human color vision processing. Influence on subjective and objective vision performances as binocular functions, fusion, stereopsis and color vision has been tested. Special colored glasses have been created, taking into account each subjects refraction for distance and tested for the 5 months adaption time. No negative influence on binocular functions, no changes of heterophoria and lowering in fusion ability and stereopsis have been stated due to use of the selective filters. Red/green isoluminant contrast perception ability and stereopsis have been stated due to use of the selective filters. Red/green isoluminanat contrast percption ability for distance improved from 0.2 m to 0.8 m individually. Subjective color perception improvement has been stated during use in adaptation time for all subjects.

The purpose of the study was to work out a method how to use the computerized Hess screen in proximal vergence measurements. Proximal vergence or vergence due to knowledge of nearness is one of four independent components making up the total vergence response. Proximal vergence is expressed as a ratio - proximal convergence/test distance (PC/T). The computerized Hess screen is usually used to detect and to measure an ocular misalignment in patients with paralytic strabismus in different directions of gaze. The computerized Hess screen can be used to assess PC/T ratio in different directions of gaze, providing the open-loop disparity vergence and accommodation systems and assuming that tonic vergence is stable. The fusional system loop is opned using red/green filter goggles, objects with different size and color, a completely darkened room, and vertical dissociation (using a prism). The accommodation system loop is opened using pinhole. The test was performed on 16 neurologically and binocularly normal subjects (14 women, 2 men; average 24 y., 20-38 y.) Average PC/T ratio in a primary position for the whole group was 2.8pd/D with a standard deviation ±0.8 pd/D, which correlates with results in literature obtained by other methods.

The critical fusion flicker frequency of the human visual system is the threshold sensitivity for a sine wave-modulated patch of monochromatic flickering light measured as a function of its temporal frequency and average luminance level. The critical flicker fusion frequency changes in different ocular and non-ocular conditions, for example: high-myopia, AMR, glaucoma, schizophrenia, after alcohol intake, fatigue. A computerized test for critical flicker fusion frequency determination was developed. Visual stimuli are two monochromatic LED light sources that are connected to a microcircuit driven by a computer program. The control of the device is realized through the parallel port of the PC. During the test a patient has to choose which one of two light sources is flickering. The critical cliker fusion frequency is determined by a psychophysical procedure, where the stimulus frequency that showed detection probability 75% is considered as threshold.

The main concepts of positional indication are discussed, and appropriate mathematical models are proposed. We analyze the features of positional data representation on the displays with different (linear and array) types of element connection. The mathematical models of digital integrated circuits for positional indication on different types of displays are presented. An optimized analytical model and applicable logic structure for display with series connection of elements are proposed.