This PDF file contains the front matter associated with SPIE Proceedings Volume 6596, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Nanoparticles of wide band gap II-VI compounds doped with transition metal (TM) and rare earth (RE) ions show fairly efficient light emission. Mechanisms of enhancement of 3d-3d (TM ions) and 4f-4f (RE ions) intra-shell transitions are discussed. It is demonstrated that quantum confinement, imposed on free carriers in nanoparticles, enhances spin dependent interactions of free carriers with TM and RE impurities. These interactions relax parity and spin selections rules for intra-shell transitions. We also show that host-to-impurity energy transfer is increased in nanoparticles, as compared to situation found in bulk samples.

We have investigated properties of poly(9-vinylcarbazole) (PVK) doped with 30% wt 4-dibutylamino-4'-nitrostilbene (DBANS), depending on orientation of the polar DBANS molecules. Appearance of the orientation-induced built-in electric field was proven optically by the solid electric field induced second harmonic generation and electrically by the current-voltage characterization. Modification of optical properties was evidenced by the spectral dependencies of the absorption coefficient. The thermally stimulated current spectra had demonstrated that carrier transport and trapping are affected, too.

Fast development of information technologies results the need to use information characteristics in order to describe the optical and optoelectronic devices. The statements formulated in the information theory for the communication systems can be also used in information optics, if the optical field digitization problem is solved. The problems which proceed from different possibilities of light signal and field digitization, are considered below.

On the basis of investigation of photoluminescence (PL) dynamics of highly excited structures with different In content under strong excitation by short laser pulses and comparison with model calculations we analyze emission mechanisms in these In-containing systems. The obtained PL spectra in various In-containing samples exhibit stimulated emission line on the short-wavelength side of the spontaneous PL band. We suggest theoretical model for optical transitions in InGaN compounds with strong compositional fluctuations leading to two distinct types of the regions, one of which is In-rich islands. We assume that optical band-gap within those two regions is randomly fluctuating with Gaussian distribution. Calculated PL spectra as a function of excitation and time are in fair agreement with experimental results demonstrating all the observed peculiarities of luminescence dynamics obtained experimentally.

We show experimentally, and interpret theoretically the conical and multiconical emission of optical parametric oscillators with seed injection in monolithic mini-cavities. We show the tunability of the conical emission angle, the switching between different resonant cones, and simultaneous emission on different cones, depending on the pump angle as well as on the length of the resonator.

The possibilities to transmit maximum amount of information for spectral devices based on acousto-optic tunable filter (AOTF) are defined not only by the AOTF selectivity and, correspondingly, by the total amount of distinguished spectral intervals but also by the device threshold sensitivity. The necessary sensitivity estimation of the photosensitive components required to provide the device operation with given selectivity has been performed. We have also described the experimental investigations of the specially designed spectral device containing an AOTF as a monochromator component. The AOTF specially elaborated for this purpose provides selection of spectral intervals with bandpass of several nm, depending on its place in the total spectral range. Information characteristics of such spectral devices have been also discussed.

Lead chalcogenide thin films have found their way in a variety of applications over the last three decades. IR-detectors based on these materials, for instance, are commercially used in microelectronics, medicine and for military applications. This work is concerned with the effect of the nanostructure on the photoelectric properties of n-type In-doped PbTe thin films. Nanostructured thin films were prepared by varying the rate of nucleation as a function of the nature and temperature of the substrates. The broken bonds at the grain boundaries generate acceptor states in n-type films, capture electrons from the interior of the grains and give rise to p-type inversion layers between adjacent grains. A model, based on the assumption the current is exclusively due to the motion of holes in the inversion channels along grain boundaries is proposed to explain temperature dependences of photoelectric properties. It was demonstrated such structure is optimal for maximizing their photoconductivity due the separation of electron-hole pairs on grain boundaries and consequently increasing the carrier life time. This approach allows designing IR-detectors based on nanocrystalline PbTe films with high sensitivity at wavelength up to 4-5 &mgr;m that do not require cryogenic cooling.

Shallowly formed InAs quantum dots (QDs) embedded in GaAs are investigated by Optically Detected Microwave Resonance (ODMR) technique. The low temperature (1.6 K) photoluminescence (PL) spectrum reveals a two-peak structure which is attributed to two different classes of QDs: smaller and larger in size. V-band (60 GHz) ODMR is selectively detected in each of the peaks and depending on the PL detection energy, a different ODMR spectrum is obtained. Detection in the high-energy band reveals a low-field negative signal which is ascribed to cyclotron resonance of the electron in the two-dimensional wetting layer, corresponding to an effective mass of 0.067 m₀. The microwave-induced signal at higher fields (~1.1 T) is tentatively attributed to magnetic resonance transitions between spin states of the holes confined in the smaller QDs. When monitoring the emission of the larger QDs, the obtained microwave-induced signal is negative while the resonance line at low field, associated with the cyclotron resonance, is no longer present. The V-band ODMR spectra are compared with W-band (94 GHz) measurements obtained for the same QD structure.

To analyze the main features of THz radiation generation caused by optical-phonon transit-time resonance a simplified analytical model is developed in terms of some generalized parameters of bulk materials and 2D structures. In the framework of such a model and direct Monte Carlo simulations an increase up to 5 times of the cutoff frequency for THz radiation generation is predicted going from 3D and 2D transport.

We had investigated effects of the high-energy proton irradiation on the properties of radiation detectors fabricated as Schottky diodes on 4H-SiC. The doses of 24 GeV protons ranged from 10¹³ cm^-2 up to 10¹⁶ cm^-2. Numbers and activities of radionuclides and isotopes produced after the irradiation were analysed. Activities of 7Be and ²²Na were found to be proportional to the irradiation dose and ranged from 1.3 up to 890 Bq and from 1.9 up to 950 Bq, respectively. The contact properties were investigated by means of the current-voltage analysis. At lower irradiation doses a slight decrease of the effective potential barrier height from about 0.75 eV down to < 0.7 eV took place. The reverse current of the diodes grew by up to one order of magnitude. At the doses above 3x10¹⁵ cm^-2 opposite changes were observed. Irradiation by up to 1x10¹⁶ protons/cm^-2, resulted in the increase of the potential barrier height up to ~ 0.85 eV, followed by the drop of the reverse current by up to two orders of magnitude. The observed effects were explained by the appearance of the disordered material structure because of the high-energy particle bombardment.

We had investigated photoelectrical and current transient properties of TlBr in the temperature region from -20 C up to +20 C, in which the effect of ionic conductivity changes significantly. The evaluated thermal activation energy value of conductivity of about 0.78 eV could stand for several mechanisms, e.g., electronic and ionic conductivity. From the spectral dependencies of photocurrent several defect-related maxima in the region between 1 and 2.5 eV were identified, being dependent on sample prehistory. Maximum at about 1.2 eV had appeared if the spectra were scanned from the high to the low quantum energies. Meanwhile the height of the maximum at about 2.1-2.2 eV used to decrease if the sample was kept biased for several hours. The transient photocurrent kinetics had demonstrated a complex behaviour that could be explained either by the combined trapping and/or recombination of light-generated carriers to the defect centres associated with potential inhomogeneities, followed by the growing ionic conduction or by a diffusion-related scattering variation in time. The evaluated thermal activation energy of the time constants of both processes was found to be 0.24 - 0.27 eV. The obtained results indicate that ionic conductivity can take place also at -20 C, though its influence is less because of the thermally activated character.

The difference between conditions of image and hologram recording is determined by the fact that in the first case the light intensity spatial distribution whereas in the second case the light wave amplitude and phase distribution is recorded. Also multiplexing is possible for the hologram recording, which increases significantly the informative capabilities of the recording. The phase recording possibility allows to create several new classes of recording media. In order to improve the media successfully, it is necessary to understand correctly the demands to them which are discussed below.

A theory of the non-steady-state photo-induced electromotive force in bipolar semiconductors accounting for the boundary conditions in a metal-semiconductor junction and distortion of energy bands near semiconductor surface is developed. It is shown that the surface potential can change essentially both the amplitude and the phase-frequency characteristic of the photo-induced electromotive force.

We have studied interband optical transitions, electronic structure and structural quality of p-type (Be) and n-type (Si) &dgr;- doped GaAs/AlAs MQWs designed for selective THz sensing applying differential surface photovoltage (DSPV) spectroscopy. Sharp derivative-like features associated with excitonic optical transitions in GaAs/AlAs MQWs have been observed in the spectra at 300 K and 90 K temperature. The energies and line broadening parameters for a large number of QW related excitonic transitions were determined from the line-shape analysis of the DSPV spectra. The spectroscopic data of transition energies were found to be in a good agreement with calculations within the envelope function approximation which took into account the nonparabolicity of energy bands. Analysis of the dependence of the exciton linewidth broadening on the quantum subband number allowed evaluate line-broadening mechanisms and interface roughness in the MQW structures. It was determined that doping with Si broadens more effectively the optical spectra lines in comparison with the structures of the same design doped with Be.

New approach to measure a magnetic component of a microwave radiation via sub-harmonic mixing in high-T_c superconductor Bi₂Sr₂CaCu₂O₈ layer kept close to the transition temperature T_c is suggested. Employing an electrical nonlinearity near the transition, we have mixed alternating electrical field of 1 MHz and 2 MHz frequencies in the sample placed on the narrow wall of the waveguide for 10 GHz frequency range. The recording principle is illustrated showing the relation between the amplitude of the mixing signal and the microwave magnetic field component in a standing wave experiment. The underlining idea is also confirmed by experimental data obtained measuring the third order nonlinearity recorded by the application of the double-modulation approach in the microwave range.

We present a comparative study of colloidal PbSe_xS_1-x alloyed nanocrystals (NCs) with variation of chemical composition and different structure (core-shell and homogeneous) prepared by a single-injection procedure with respect to corresponding PbSe core NCs and PbSe/PbS core-shell NCs prepared by the traditional two-injection procedure. The narrow band edge of absorption and photoluminescence 1S-exciton energy of PbSe_xS_1-x alloyed NCs were tuned (blue shifted) from the band edge of the same size PbSe NCs to the band edge of PbS NCs by controlling the Se+S/Pb molar ratio in the synthetic mixture. The magnitude of the Stokes shift was found to be dependent upon the size of NCs and on the core(shell) chemical composition. The largest Stokes shift (100 meV) was observed in the smaller PbSe NCs, while PbSe_xS_1-x core-alloyed shell NCs prepared by a single-injection procedure show the vanishing small Stokes shift.

Silver nanoparticles have received considerable attention due to their attractive physical and chemical properties. The surface plasmon resonance and large effective scattering cross section of individual silver nanoparticles make them ideal candidates for molecular labeling, where phenomena such as surface enhance Raman scattering (SERS) can be exploited. In addition, silver nanoparticles have recently been shown to be a promising antimicrobial material. In the present research silver colloid was produced by sodium citrate reduction. The colloidal silver was incorporated by dip-coating to the polymer substrate. X-Ray Fluorescence Spectroscopy (XRF), Atomic force microscopy (AFM), ultraviolet-visible spectroscopy (UV-VIS ) and SERS indicate that the produced structures include metallic crystalline silver nanoparticles. The surface plasmon resonance peak in absorption spectra of silver particles showed an absorption maximum at 420-500 nm. The silver - polymer nanocomposites structures with selective light properties as a result of plasmon resonance shifting in the UV-VIS wavelength region were produced.

Detection peculiarities of an un-cooled (room temperature) 8x8 pixel array designed to image broadband THz radiation were investigated. Each pixel consists of a thin conductive film absorber on a dielectric membrane with thermopile temperature readout. It was designed and tested for four combinations of two different types of absorber and thermopile materials. The photo-response profile, determined by scanning the pixels through the focus of a THz laser beam, was wider than expected from a 2-D convolution of the Gaussian beam and the absorber surface. Also the time response did depend on the position of the beam relative to the pixel. Simulations show that those properties are due to the fact that also the thermopiles absorb THz radiation. For the best composition of absorber and thermopile, the responsivity, the noise equivalent power, and the bandwidth were estimated to be of 28 V/W, 5x10^-9 W/Hz^1/2 and 50 Hz, respectively.

We have developed PC controlled dot-matrix holographic recording system based on the CW diode pumped YAG:Nd SHG laser (wavelength 532 nm, power 30mW,) modulated electronically with TTL signals. Two-beam technique has been used with convergence angle 30^o and PC controlled incident beam plane rotation 0-360^o. Optical system consists of beam splitter, 40mm focus length forming cylindrical lens and 40mm focusing lens. Characteristic parameters of experimental equipment are following: spot size - 50-200 micrometers, direct laser writing area, limited by x-y positioning system, was 70mm x 70mm, number of writing head rotation positions up to 256 (8 bit), time of each exposure - 1-1000 msec. As the recording material we have used As_xS_ySe_1-x chalcogenide glass material. Diffraction efficiency of written gratings in the material in dot-matrix regime exceeds 25%. Original method for surface relief enhancement by etching and subsequent electroplating has been developed. Special PC controlled device for thermal imprinting of relief holograms on the metallized polyamide film has been built. Measurements of light transmission, reflection, and diffraction phenomena of laser beams in processed chalcogenide materials are discussed.

We present comprehensive experimental study of p-type (Be) and n-type (Si) &dgr;-doped GaAs/AlAs multiple quantum wells (QWs) intended to be used as selective sensors/emitters in terahertz (THz) range. The structures of various designs and doping levels were studied via different optical-photoreflectance-, surface photovoltage- and differential surface photovoltage. spectroscopies and a THz photocurrent technique using as THz emission source either free electron- or optically-pumped molecular THz laser within 4.300 K range of temperatures. Analysis of Franz-Keldysh oscillations in photoreflectance spectra and line shapes of the differential surface photovoltage spectra enabled to estimate built-in electric fields and excitonic parameters for a large number of QW subbands. The experimental interband transition energies were compared with calculations performed within the envelope function approximation taking into account non-parabolicity of the energy bands. The dominant exciton line broadening mechanisms were revealed, and the interface roughness was evaluated from analysis of the dependence of exciton linewidth broadening on the QW width. Terahertz spectroscopic measurements in p-type structures have indicated strong absorption around 55 &mgr;m wavelength due to intraband absorption of the bound holes, while increase in photocurrent in the structures below 80 &mgr;m wavelength is caused by photothermal ionization of Be acceptors.

Indium-tin oxide (ITO) is the main material for making transparent electrodes in electronic devices and flat panel displays. Laser-direct-write technology has been widely used for patterning ITO. The well defined edges and good electrical isolation at a short separation are required for the modern OLED and RFID devices of high packing density. High repetition rate lasers with a short, picosecond pulse width offer new possibilities for high efficiency structuring of transparent conductors on glass and other substrates. The results of patterning the ITO film on glass with picosecond lasers at various wavelengths are presented. Laser radiation initiated ablation of the material, forming trenches in ITO. Profile of the trenches was analyzed with a phase contrast optical microscope, a stylus type profiler, SEM and AFM. Clean removal of the ITO layer was achieved with the 266 nm radiation when laser fluence was above the threshold at 0.20 J/cm², while for the 355 nm radiation the threshold was higher, above 0.46 J/cm². The glass substrate was damaged in the area where the fluence was higher than 1.55 J/cm². The 532 nm radiation allowed getting well defined trenches, but a lot of residues in the form of dust were generated on the surface. UV radiation at the 266 nm provided the widest working window for ITO ablation without damage of the substrate. Use of UV laser radiation with fluences close to the ablation threshold made it possible to minimize surface contamination and the recast ridge formation during the process.

Planar microwave detectors on the base of modulation doped AlGaAs/GaAs structures with &dgr;-doped layer were investigated in (26÷120) GHz frequency range. Comparison of the features of the microwave diodes on the base of modulation doped structures with &dgr;- and smoothly-distributed doping impurities in the AlGaAs barrier is presented. Influence of the layers composing the modulation doped structure onto detective properties of the microwave diodes is ascertained both theoretically and experimentally. In the case of the structure with &dgr;-doping this influence was less, especially, in the case of symmetrically shaped structure with n-n⁺ and homogeneous asymmetrically shaped modulation doped structure.

Spin precession of a ballistic-hole when external magnetic field is absent and when the hole freely propagates in either heavy- or light-mass band is considered. The spin precession is due to linear in wave vector terms in the Luttinger-Kohn Hamiltonian. It was found that in contrast to conduction-band the valence band spin precession orbits are not circular. They are either ellipses or lines for light- and heavy-holes, respectively. The results of the paper can be applied to describe hole spin-dynamics in A₃B₅ compounds, for example, in simulation of spin-FETs by Monte Carlo method.

The results of both analytical and numerical study of the optical damage of a solid nano-size particle, partly ionized by an ultra-short laser pulse (USLP) are presented. The comparison of the results that has been obtained analytically and numerically shows that the proposed method allows to describe the main features of nano-particle damage induced by Coulomb forces, that arise in solid due to the charge equilibrium distortion under USLP action. The kinetics of energy spectra of the spreading ions has been analyzed taking into account the Coulomb repulsive forces and the retarding processes that restrict ion motion inside the particle.

Ablation characteristics of chromium thin film on a glass substrate by nanosecond laser pulses were investigated. The laser beam was tightly focused through the glass substrate to a stripe-like spot using the acylindrical lens. The metal was removed only by the central part of the laser beam, where local laser fluence exceeded the well-defined ablation threshold. Formation of a wide area cleaned by the series of laser pulses caused some side effects. The stripe ablated by a single laser pulse had sharp edges on both sides, while the partially overlapping pulses formed a wide stripe with a complicated structure made of the remaining metal. Regular structures, ripples, were developed when laser fluence was slightly above the threshold and the shift between pulses was less than a half width of the line ablated by a single laser pulse. The ripples were located periodically (~4 &mgr;) and were orientated perpendicularly to the long axis of the beam spot (in parallel to the laser pulse shift direction). Their direction did not depend on the laser beam polarization. Different models of the ripple formation in the thin metal film were considered, and instability of the moving vapor-liquid- solid contact line during evaporation of thin liquid films appear to be the most appropriate process responsible for the observed phenomena. Regular gratings with the unlimited line length can be produced by using the technique.

Time-integrated and time-resolved FWM techniques were applied for characterization of the photoelectrical properties of undoped, S-doped, and Fe-doped InP wafers and for a mapping of their homogeneity. We performed measurements of spatial distribution of diffraction efficiency across the wafers by nanosecond FWM and investigated a physical origin of the observed variations by using time-resolved picosecond FWM. By analyzing the diffraction efficiency kinetics and its dependence on excitation energy, we evaluated the impurity-assisted carrier generation, recombination, diffusion processes, electrical activity of the defects, and their distribution across the wafers. Carrier lifetime variation from 2.5 ns to 7.5 ns across the undoped InP wafer was found, while the diffusion coefficient value of 8 ± 0.5 cm²/s was almost constant. In S-doped InP wafer, wafer inhomogeneity was attributed to carrier generation peculiarities governed by spatial distribution of deep centers.

Non-equilibrium carrier generation, transport, and recombination have been investigated in Fe-doped InP crystals experimentally in subnanosecond time domain by using time-resolved picosecond four-wave mixing technique. The carriers were generated by below band-gap excitation at 1064 nm (hv = 1.17 eV), what allowed photoexcitation of non-equilibrium carriers from/via Fe-related deep levels. The contributions of Fe²⁺/Fe³⁺ deep level states and of the excited state Fe^2+* have been analyzed by numerical modeling, using the relevant model which took into account carrier generation via different defect states, as well recombination and diffusion. The modeling was helpful to get insight into varying with excitation generation rates of holes and electrons and explained the main features of FWM kinetics and exposure characteristics.

A portable fibre-optic spectrometry set-up has been assembled and tested for applications in skin diffuse reflectance spectrometry, laser fluorescence spectrometry and multi-wavelength reflection photoplethysmography (multi-PPG) studies. The spectrometry set was tested by diffuse reflectance and fluorescence measurements for diagnostics of skin vascular malformations and pigmented diseases such as nevi and melanoma. In addition, studies of microcirculation in blood vessels located at different depths from the skin surface were performed by the multi-PPG method. The results of skin diffuse reflectance and autofluorescence showed differences in spectra of healthy and pathologic skin. The parameter ratio "pathologic/healthy" has been calculated in order to check the possibility of quantifying the specific pathology. The autofluorescence fading effect was observed. Our studies of the blood volume pulsations confirmed the possibility to separate the time-variable PPG component from the total skin diffuse reflectance signal.

Fundamentals, design, and operation of a fiber-optical non contact reflection displacement sensor having two identical fiber optical pairs A and B in separate holders are presented. The main principle of operation of the sensor is an artificially organized crossing point of output signals A and B when the reflection body surface is displaced. The output signal (A-B) of the sensor is proportional to the displacement direction of the reflecting body surface from the fixed zero position and depends on the body reflection coefficient, light source intensity, and loss in the fibers. The output signal (A-B)/(A+B) is not dependent on the body reflection coefficient, light source intensity, loss in the fibers. This was confirmed not only theoretically, but also experimentally. The sensitivity S_sub of the sensor was considered to be as high as possible of this type of sensors.

Investigation and comparison of modeling and experimental results for the two-fiber reflection non contact displacement sensor are presented. The main aim of the research carried out here is to compare the two light emitting fiber constants obtained in the experiment and those obtained in the modeling process and set their values for the super light diode (SLD) and laser diode (LD) type sources. In the research paper the constants k and m (describing the distribution of the light emitting source beam intensity) values obtained, alongside with which a rather good match of the experiment and modeling results was obtained. In addition, the work presents some comparisons with the beam waist calculations in which the beam waist depends on the light wavelength &lgr;. The results of research have shown that it is possible to calculate the characteristics of fiber sensors precisely enough by means of modeling. The results obtained were used in the new compensation type two-fiber optopairs sensor.

Novel highly concentrated Yb/Er and Nd phosphate glasses were elaborated and microchip lasers were produced. Lasing parameters of Yb/Er and Nd phosphate glasses were studied. Novel type of radiation excited by pumping power sufficiently high for amplification of radiation but lower than lasing threshold was observed. It was found that indicatrix and spectrum (comb spectrum) of this radiation differed from the parameters of both luminescence and lasing radiation. It was found that the modulated radiation emitted by the micro-chip lasers was super luminescence. Spectral separation between adjacent lines of comb spectrum varies with radiation wavelength, length of Fabry-Perot resonator and refractive index of amplifying medium. The phenomenon of super luminescence modulation in Fabry-Perot micro resonator can be used for designing the simplest comb spectral channels generators for DWDM working in 0.9-1.6 &mgr;m spectral range. 200 and 250 spectral channels were realized for Yb/Er and Nd microchip lasers, correspondingly.

The transmission light intensity dependences of different silica glass fibres have been experimentally studied when nanosecond pulse trains were incident. A pronounced 13-42% transmission increase was found in contrast to the picosecond pulse irradiation when a monotonic transmission decrease took place. The photoinduced transmission increase is explained in terms of photothermally increased numerical aperture, the photothermal lens effect, and the photoinduced saturation of a weak impurity absorption. The obtained results can be applied in high power applications of fibres such as WDM fibre communication systems.

The phase change caused by excitation of surface plasmons (SP) in a Kretschmann configuration was measured by a rotating polarizer scheme using commercial spectral ellipsometer (GES5, SOPRA, Co). The setup was used to determinate the optical constants at 800 nm of an octadecanthiol (ODT) with a thickness of 9 nm on a gold film. The numerical values n=0.18, k=3.44 for the Au film, and n=1.4 for ODT were obtained by a best-fit procedure to experimental data. From model calculations it is argued that in thin-film cases SP phase measurements give more precise values for the optical constants than conventional ellipsometry and SP amplitude methods. Combination of SP method with advantages of phase measurements of ellipsometry showed sufficient increase in sensitivity (more than one order of magnitude). This methodology could be used for detection of monolayer and even submonolayer films on metals.

A new approach to control chemically the atomic structure and electronic properties of III-V compound semiconductors is developed. This approach is based on the modification of chemical properties of anionic adsorbates (such as HS^- ions) prior to their adsorption on the surface. This is achieved through the solvation of the ions with different amphiprotic solvents (water, alcohols). Ab initio quantum-chemical calculations show that the reactivity of solvated HS^- ions depends essentially on composition of the solvation shell: hydrated ions are slightly electrophilic, whereas ions solvated by alcohols are nucleophilic. Mechanism of interaction of such solvated ions with the semiconductor surface depends on the solvent solvating the ion. Experimentally it is found that on adsorption of HS^- ions from different solvents the As-S bonds with solvent-dependent ionicity are formed on the surface. These surfaces possess different ionization energy and electronic properties though now traces of solvent molecules are found in XPS spectra.

In our previous work was showed that the SPR technique is very effective for in situ observation of the lipase interaction with MNFcP (9 merkaptononyl - 5' - ferrocenylpentanoate). However, the investigation was performed with only monochromatic 633nm light at the beginning and at the end of the reaction. In this work, the results of the investigation of the reaction kinetics using a tunable light source (&lgr;=600÷1400nm) are presented. Spectral measurements were accomplished with a commercial spectral ellipsometer GES-5 (SOPRA, France). It was demonstrated that this method is sufficiently sensitive for lipase interactions with a thin MNFcP layer (d=3.65nm). It was concluded that the experimental plasmon minimum shift is due to lipase sorption on the MNFcP and, as a result, causes an increase in the effective layer thickness. These results are important in understanding the interaction of these molecules and in determing their size and distribution on the surface.

Composite system of iron porphyrin (FeTPPS) on aminosilanized Si substrates was investigated by studies of surface morphology and optical response. Aminofunctionalized siloxane films on silicon substrates were produced from different sol-gel precursors prepared from 3-aminopropyltriethoxysilane (APTES) dissolved in water, ethanol and acetone. Immersion technique was used for the formation of APTES films. Aqueous solutions of FeTPPS were deposited on aminosilanized Si substrates. Topographic features of nanostructures in composite FeTPPS/APTES/Si system were investigated by atomic force microscopy (AFM) technique. High-resolution phase contrast imaging revealed the substructure of siloxane films on silicon substrates and nanoaggregates of FeTPPS immobilized on aminosilanized Si surface. Spectroscopic ellipsometry measurements were carried out in the region 1-5 eV in order to characterize the siloxane films and composite structures. The analysis of obtained results allowed one to conclude that FeTPPS molecules were attached to the surface by covalent bonds between the functional group of sulfonic acid SO₃^- of iron porphyrin and (-NH₂H⁺)-group of APTES.

We present a study of phonon sidebands in the photoluminescence spectra of Be acceptor-doped GaAs/AlAs multiple quantum wells at liquid nitrogen temperature. Up to two phonon satellites with a separation close to the GaAs longitudinal optical phonon energy are observed in the sideband of the photoluminescence. A theoretical analysis of the satellite-related photoluminescence lineshapes and their energetic position and impurity induced spectra is presented. The results show that the phonon satellites can be attributed to free-electron-Be acceptor transitions involving longitudinal optical phonon of GaAs - the host material of the studied quantum wells.

In this article we present results of an investigation the PL properties of highly Si &dgr;-doped GaAs/AlAs multiple QWs at liquid nitrogen and room temperatures. We discuss possible mechanisms for carrier recombination in the QW structures placing particular emphasis on the origin of the low energy tail in the PL spectra, and its features.

In this presentation we analyze three different techniques devised to measure dispersion of chirped mirrors. These methods are direct GD measurement, one-dimensional spectral interferometry and Fourier analysis of white light cross correlation. Each method was tested with the same samples in order to find out their advantages and limitations. It was find out that from the investigated methods the Fourier analysis of white light cross correlation is the most suited technique for fast and accurate dispersion measurement.

Two-terminal diode-like porous silicon structures have been investigated under the impact of strong electric field. Strong electric field I-V current-voltage characteristics have been measured in pulse regime by applying electric pulses of 15 ns duration, at repetition rate of (100-150) Hz, creating average electric field in the structure up to (10³-10⁴) V/cm. Modification of structured state of the structures have been revealed at strong electric field influence, resulting in change and stabilizing of their series resistance.

Properties of titanium dioxide thin films grown by atomic layer deposition from TiCl₄ and H₂O on SiO₂ substrates were characterized using Raman spectroscopy and spectrophotometry methods. Raman spectroscopy revealed transformation of the film structure from amorphous to anatase, to anatase/rutile mixture and then back to anatase with the increase of deposition temperature from 100 to 680^oC. Variations in the growth rate, refractive index and extinction index accompanied these structural changes. Analysis of the transmission curves demonstrated that differently from amorphous films, the crystalline films were optically inhomogeneous in the growth direction.

Reversible resistance change of thin La_0.67Ca_0.33MnO₃ films, grown on cleaved MgO substrates, have been investigated using both dc current and nanosecond electrical pulses of 10 ns and 100 ns in duration. It was found that at T=80 K the series of 10 ns pulses with electric field strength above 20 kV/cm induced a reversible change of the film from low to high resistive state. At the same time, the series of 100 ns pulses transmitted through the sample with increased resistance induced an inverse effect - i.e. transformation of the film to the initial state. It was also obtained that at 130 K (just below Curie temperature T_c) the series of 100 ns electrical pulses induced the resistive transition at lower electric field value (13.7 kV/cm). The obtained results were explained in terms of local film heating and strong electric field effect on narrow conductive constructions during current flow through channels in electrically inhomogeneous media in the vicinity of T_c.

Thin films in the Cr-Ti-O system were atomic layer deposited from CrO₂Cl₂, TiCl₄, and CH₃OH on Si(1 0 0), fused SiO₂, and a-Al₂O₃(0 1 2) substrates at 420 ^oC. The proportion between Ti and Cr resulted from the ratio of the CrO₂Cl₂/CH₃OH and TiCl₄/CH₃OH pulsing. The films were grown up to the thickness of about 70 nm. Annealing of the films was performed in O₂ at 1000 ^oC. A notable dependence of their microstructure, conductance, and conductometric response to CO, H₂, and CH₄ in dry air on the substrates, Ti content, and annealing has been demonstrated. The films were polycrystalline on Si and SiO₂, and epitaxial on a-Al₂O₃. At temperatures above 400 ^oC, the films had a conductance, advantageous from the point of view of semiconductor gas sensors. In response to a 30-ppm CO exposure at 450 ^oC, an annealed film on the a-Al₂O₃(0 1 2) substrate, distinguished by a relatively high Ti/Cr atomic ratio, showed a 16-% conductance decrease in 20 s, with a 120-s recovery.

We have derived and analyzed the wavefunctions and eigenstates for quantum wells (QW), broadened due to static interface disorder, within Discreet Variable Representation (DVR) approach of Colbert and Miller. The main advantage of this approach, which we have tested, is that it allows to obtain ab-initio and to analyze the shift and broadening of resonance states in a semiconductor quantum wells of different shapes. Calculations based on the convolution methods were used to include the influence of disorder to the formation of heterojunction interfaces.

A mechanism of formation of graded band-gap based on Thermogradient Effect (TGE) is proposed in Cd_1-xZn_xTe at irradiation by second harmonic of a Q-switched YAG:Nd laser. According to the effect, the interstitial atoms of Cd (Cd_i) in Cd_1-xZn_xTe move along the temperature gradient while the Cd vacancies (V_Cd) and Zn atoms - in the opposite direction, into the bulk of the semiconductor where temperature is lower. Photoluminescence (PL) spectra studied at 5 K show that concentration of Zn atoms increases due to aggregation of VCd with Zn after laser irradiation. Formation of a graded band-gap in Cd_1-xZn_xTe crystal at irradiation by second harmonica of YAG:Nd laser by is shown to be possible.

We propose a double injection current transient technique to study the charge carrier mobilities and recombination in thin films of bulk heterojunction structures. This experimentally simple technique allows estimation of bimolecular recombination coefficient and charge carrier mobility, either of a sum of electron and hole mobilities in double injection into insulator mode, or the ambipolar mobility in semiconductor mode. The double injection current transient technique is used to study RRPHT/PCBM bulk heterojunction solar cells, and the obtained results are compared with results obtained using TOF and CELIV techniques.

Sub-bandgap light recording (SBLR) of holograms is studied basing on the experiments in a-As₂S₃ films and literature data. Holographic grating recording with focused (light intensity I = 14 - 124 W/cm² ) and unfocused (I = 0.50 - 0.78 W/cm²) 632.8 nm He-Ne laser sub-bandgap light in non-annealed and annealed a-As₂S₃ films has been experimentally studied. The focused light recording is found to be much more efficient (diffraction efficiency up to 14.9%, specific recording energy down to 216 J/(cm²%)) than the unfocused light recording (0.11%, 72400 J/(cm²%)). Some other properties are also different. The focused light recording is explained by the photothermally stimulated relaxational structural changes (RSC) accompanied by the photoinduced generation and recharging of D-centers. The unfocused light recording is explained by the photorientation of D-centers with some contribution of RSC . SBLR in materials other than a-As₂S₃ films was considered and the conclusion was made that amorphous sulfides and selenides are expected to be the best SBLR recording materials. SBLR is advantageous because of its bulk nature enabling the production of homogeneous holographic optical volume elements and devices.

Amorphous carbon films were formed on Si (111) wafers from argon-acetylene gas mixture at atmospheric pressure by direct current (DC) plasma torch discharge. The Ar/C₂H₂ gas volume ratio varied from 12 to 100, and the distance between plasma torch nozzle exit and the samples was 0.005, 0.01 and 0.02 m. SEM revealed carbon coatings thickness in the range of 20-270 &mgr;m, and variation of the growth rate from 0.067 &mgr;m/s to 1.5 &mgr;m/s. Growth rate of the coatings increases decreasing Ar/C₂H₂ gas ratio and the distance. The Raman spectra of carbon films indicate the upward shift of the D (~1360 cm^-1) and G (~1600 cm^-1) peaks, compared to typical diamond-like carbon (DLC). a-C:H coatings deposited at higher Ar/C₂H₂ gas ratio (60 and 100) and distance d greater than or equal to 0.01 m contain high sp³ bond fraction and are attributed to DLC films. However Raman spectra shape and ID/IG ratio demonstrate existence of diamond phase mixed with glassy carbon phase. Films produced at lower Ar/C₂H₂ ratios are graphite-like carbon (GLC). The Fourier transform infrared (FTIR) spectroscopy has shown that film transparency increases decreasing acetylene gas content. Reflectance of the films depends on Ar/C₂H₂ gas ratio and distance, and varies from 60% up to 90%. The IR spectra showed clear evidence of C=C and C=O bonds in GLC films and presence of sp³ CH₂ symmetric (2850 cm^-1) and antisymmetric (2920 cm^-1) modes in DLC coatings.

Magnetic circular dichroism of iron porphyrin aqueous solutions was studied using a photometric ellipsometer with photoelastic modulator of light polarization in the spectral range 350-750 nm in magnetic fields up to 350 mT. Buffered aqueous solutions of iron porphyrin with pH-values equal to 1.7, 3.6 and 6.8 and concentration 0.1-1.0 mM were prepared by dissolving Fe(III) meso-tetra(4- sulfonatophenyl)porphine chloride. The spectra of magnetic circular dichroism were observed in the region of Soret band (390-420 nm) and Q-bands (500-700 nm). The lineshape analysis of magnetic circular dichroism spectra has shown that A-terms were dominant though a significant overlap masked the fine structure of the Q-bands. The magnetic circular dichroism signal was of order 1x10^-2 cm^-1/T in a linear approximation with respect to magnetic field. The data indicated that complete lifting of the degeneracy of the states involved in the corresponding optical transitions did not occurred in magnetic fields used. The model of the ground and excited states in iron porphyrin was discussed.

Ion-induced reduction of dislocation mobility in LiF crystals irradiated with swift heavy (U) and light (Ni) ions of a specific energy of 11 MeV per nucleon at fluences between 10⁶ and 10¹¹ ions/cm² was studied. The arm length of dislocation rosettes produced by indentation on (100) irradiated surface was measured. It has been found that in the case of heavy ions the threshold fluence (10⁶ ions/cm²) for impeding of dislocation arms is about 3 orders of magnitude lower than that for light ions. The results indicate that ion-induced defect aggregates play the dominating role in the impeding of dislocations. Heavy ions, which produce defect aggregates in the track core, cause also a stronger effect of dislocation impeding and surface hardening. In the case of light ions, the reduction of dislocation mobility is observed at higher fluences (>10⁹ ions/cm²) where the defect aggregates are created in the halo by neighbour track overlapping. The results show that fast heavy ions are suitable for nanoscale structuring and surface modification of materials.

Electronic and geometrical structures of Co_n (n=4, 6, 8) particles have been studied using both the density functional theory and the Hartree-Fock calculations. Structural differences to the corresponding clusters are presented. Four-fold coordination of the Co atoms was found to be a particularly preferable coordination environment in small Co_n species. The key element of the Co particle is suggested.

Interference coating for infrared spectral region required the transparent optical films with different refraction indexes and minimal an absorption factor. It is well known¹, that chalcogenide materials based on sulphide and selenide are the perspective film's forming materials for manufacturing of the interference coating (IC). Among the known materials, the minimal absorption factors have arsenic chalcogenide films. The value of optical losses due to absorption and scattering of the quote wave films of As₂Se₃ on 10 microns wavelength is less than 10^-5. It allows using them for manufacturing of the high quality optics in wide optical region, including optics for CO₂ powerful lasers¹. Despite of good operational characteristics and the small optical losses, many of known chalcogenide materials have not received a wide distribution. One of the reasons of that is the absence of the data of their film's optical constants (OC) of these substances, which strongly depend on a way and conditions of manufacturing and are different from OC of initial monocrystals. In the present work was investigated the optical constants of the chalcogenide films (As₂Se₃, AsS₄, AsSe₄, AsS_16.2 Se_16.2) in 0.5-2.5 (micron)m spectral range.

A quest for higher laser powers is one of the main driving forces in development of laser technology. Unfortunately all laser components have some limit to the intensity of optical radiation that can be applied on them - the so-called laser-induced damage threshold (LIDT). To enable further power scaling of laser devices, novel highly resistant optical components have to be developed. Such components are laser crystals, mirrors, fibers and other components typically coated with periodic dielectric layers made using e-beam, sputtering or sol-gel technologies. The production materials and methods of all the mentioned optics are under constant development, which requires a reliable quality test to provide the feedback to the manufacturing process; one of such tests are the measurements of LIDT. LIDT measurement procedure using repetitive laser pulses, as described in ISO 11254-2 standard, is time- and human resource consuming, if performed without automation. We developed an automated station for the measurements of LIDT that greatly reduces the required human resources and allows fast data collection. In this presentation, we briefly describe the main components of this automated LIDT test station. Furthermore we present the comparison of the latest results obtained on LIDT measurements of ZrO₂/SiO₂, Nb₂O₅/SiO₂, Ta₂O₅/SiO₂ and TiO₂/SiO₂ periodic high reflecting dielectric layers performed using repetitive nanosecond laser pulses.

We report standardized absorption and scattering losses measurements of the nonlinear crystals LiInSe₂ and LiInS₂ in IR range by high average power 1064 nm radiation and tunable radiation of optical parametric oscillator (OPO) based on a periodically poled lithium niobate (PPLN) pumped by a diode-pumped, Q-switched TEM₀₀ mode Nd:YVO₄ laser operated at 1064 nm.

Features of dielectric response to frequencies in the 0.25.1000 Hz range in ceramic samples of BaBi₂Nb₂O₉, Na_0,5Bi_8.5Ti₂Nb₄O₂₇, Na_0,5Bi_8.5Ti₂Ta₄O₂₇, and K_0,5Bi_8.5Ti₂Nb₄O₂₇ compounds are reported. Considerable relaxation of &egr;'(T) and &egr;"(T) maximums has been observed at all frequencies in BaBi₂Nb₂O₉. Na_0,5Bi_8.5Ti₂Nb₄O₂₇ and Na_0,5Bi_8.5Ti₂Ta₄O₂₇ are characterised by broad maximums on &egr;'(T) at frequencies below 100 Hz and a weak anomaly in K_0,5Bi_8.5Ti₂Nb₄O₂₇ at temperatures well below the paraelectric phase transition. Increasing values of &egr;' are observed at low temperatures in compounds containing sodium. The observed features of dielectric response are explained by largescale charge fluctuations in layered ferroelectrics.

In present study DLC films were deposited by direct ion beam deposition. Hexamethyldisiloxane vapor and hydrogen gas mixture, mixture of the hexamethyldisiloxane with acetylene as well as acetylene gas alone has been used as a source of the hydrocarbons. Optical properties of the synthesized films were investigated by spectroscopic ellipsometry. Structure of the DLC films has been studied by means of the Raman spectroscopy. Effects of the technological deposition parameters such as composition of the gas precursors, ion beam energy, ion beam current density were considered.

Measurements of dielectric permittivity show that laser-induced damage in potassium dihydrogen phosphate crystal increases its phase transition temperature and real part of dielectric permittivity of damaged crystal is lower at all measured temperatures. The largest difference between dielectric permittivity of damaged and virgin samples we observed at temperatures below phase transition temperature. It can be caused by pinning of domain walls to the crystal defects in the crystal bulk damaged by high power, nanosecond laser beam.

The performance of optical coatings for UV region (200-300 nm) is closely related to their optical losses. There are a few factors which significantly influence the extinction of deposited coating - deposition vacuum, contamination from filaments of e-beam guns, ion source and finally, the optical properties of selected deposition materials. In this work the contribution of these different factors was investigated and evaluated. HfO₂, Al₂O₃ and SiO₂ are the most widely used materials for producing UV optical coatings down to 200 nm. Influence of background oxygen pressure during HfO₂ and Al₂O₃ deposition was evaluated which enabled to reduce extinction of the deposited UV optical coatings.

This investigation was aimed at optimization of optical properties, stability and radiation resistance of optical coatings deposited using the standard vacuum coating plant equipped with the ion source for ion assisted deposition. There are some reports showing that porous dielectric coatings are more resistant to intense laser radiation, however they have smaller environmental stability than denser coatings, which are more sensitive to laser radiation. The influence of important technological parameters (deposition rate, substrate temperature, energy of ions) on optical properties and radiation resistance of high reflection dielectric coatings based on Nb₂O₅/SiO₂ and Ta₂O₅/SiO₂ in VIS spectral region is presented.