A theoretical study of two-wave polarization spectroscopy signal dependencies on crossing angle is presented. The quantitative expressions are obtained, which are in good agreement with the experimental data. The advantages of free-coordinate operator method are illustrated under treatment of band-gap formation in anisotropic stratified periodic structure problems. A method for radiation control based on pumping wave polarization tuning is proposed.

Optical and electric properties of doping superlattices, or n-i-p-i crystals, can be varied in a wide range under excitation and through the choice of the thicknesses and doping of the crystal layers. Some basic results concerned the transformation of the electron energy spectrum of doping superlattices are summarized. Parameters and characteristics of doping superlattices related to optoelectronics devices, such as photodetectors, laser diodes, and optical modulators, are presented.

Time evolution of the intensity of light diffracted by phase grating which is induced by thermal dynamic grating (TDG) in liquid film between glass or quartz substrates is studied theoretically and experimentally. Due to heat exchange at the film boundaries the thermal gratings are also formed in substrates. The diffraction intensity of substrates can be less or comparable to that of film (non-active and active substrates, respectively). The experimental results are in a good agreement with the theoretical calculations carried out for the case when the film thickness is less the TDG period. It is shown the essential influence of the film thickness and the active-substrates contribution on the evolution of the intensity of diffracted light.

The considerations of waveguiding are analyzed in isotropic absorbing film systems. In this case all propagation constants become complex numbers and dispersion relation for guided modes differs from the mode equation of the lossless waveguide. The existence of absorption causes measurable shifts of the propagation constants of the free guide modes and ones in the presence of prism coupler. It is shown how the coupling strength is modulated by the absorption of asymmetric slab waveguide.

In this work it is reported about the further development of the intracavity method of the solid state surface processing by the laser radiation. It is experimentally shown the possibility to form 2D periodical micron and submicron surface structures, looking as a system of squares, rectangles and parallelograms. A new type of the laser cavity allowed to fabricate a system of regular microhollows with submicron characteristic sizes even by means of the carbon dioxide laser treatment (10.6-micron radiation wavelength).

In this paper a theoretical consideration of quasi-steady- state generation of dye lasers (DL) with an isotropic Fabry- Perot-type resonator and coaxial (longitudinal) laser pumping is presented for the regime of saturation in the orientation distribution of excited molecules. Our analysis is carried out for cases of parallel and orthogonal mutual orientation of dipole moments of transitions with absorption and emission in dye molecules. The effect of intensity and polarization state of longitudinal pumping on the degree of linear polarization and output intensity of DL has been clarified. A preference of circular pump polarization occurs in our theory. The comparison of the results obtained with the experimental studies is also performed.

The effective nonlinear coefficients, tuning curves, angular and spectral phase-matching widths are calculated for all possible types of optical parametric generation in the principal planes of biaxial KTP crystal at Nd:YAG ((lambda) _p equals 1.064 micrometers ) laser pumping. The plots presented enable the maximal nonmonochromaticity and radiation divergence to be found for any value of the signal wave and different interaction types. We developed a numerical simulation of nonstationary optical parametric generation by solving the cut-off system of coupled equations, which describes the three wave interaction in oscillator cavity, partially filled with KTP crystal. The dependencies obtained demonstrate the dynamics of signal pulse generation development. The optimal crystal and resonator parameters were found to ensure the maximal optical parametric oscillator efficiency.

For the purpose of determining the higher-order nonlinear optical susceptibility the diffraction method based on investigation into the Fourier-expansion spatial components for the anharmonic grating of a refractive index has been used. Condition of the second-order Bragg diffraction is satisfied through doubling of the recording-wave frequency. This variant of diffraction method has been theoretically studied for the resonant media modeled by three- and four- level schemes taking into consideration the transitions between the molecular excited states. Experimentally, the method proposed for measurements of the higher order nonlinearities has been realized with the use of the six- wave mixing of monopulse YAG laser radiation in the solution of polymethine dye.

Force exerted on a microobject by the focused laser beam can be as high as the gravity force acting on the object or even significantly higher. This implies that the laser light can be used to manipulate small objects (range size approximately 0.1 - 100 micrometers ) within a suitable immersion medium. This possibility is of a great practical importance, for example, for microbiology and molecular biology (manipulation of single living cells, cell organelles, chromosomes, etc.) as well as for micromachinery and other technical branches. We use a ray-optics-based model to determine the magnitude of forces exerted by laser light as the functions of laser beam, object and surrounding medium parameters. We study the influence of these parameters on the total force in order to find the optimal parameter combination for the most effective manipulation. We have employed these theoretical results in practice and succeeded in building up a 3D laser trap which we use to manipulate divinylbenzen spherical particles (10 - 35 micrometers sized) and also irregularly shaped living protozoa cells in water medium.

We suggest a modification of a single-beam optical trap built in a conventional microscope (not the inverted one). Our enhancement of the trapping efficiency consists of a highly-reflective-layers-coated glass plate forming the bottom of the sample cell. Using this, we obtain a combination of two beams--the incident one propagating downward and the reflected one propagating upward--which together create an effective microobject trap. Using the micron-size polystyrene spheres we have experimentally proved that it is easy to achieve an efficient 3D trapping using even highly aberrated beams although the single beam trap does not work in this case. The interference of the incident and reflected beams forms a standing wave which is especially useful for nanoobjects trapping. Nanoobjects of diameters equal to tens of nanometers are stably trapped near the antinodes (intensity maxima) of the standing wave due to the restoring dipole force which is thousands times greater than the scattering force in this case. The paper presents the qualitative description of the trapped object behavior, theoretical study and calculations of forces acting on the microobjects and nanoobjects. The influence of the standing wave on the observed microsphere behavior is also discussed.

We suggest an atomic dipole trap which is produced by two counter-propagating Gaussian beams with different waists. This set-up creates an intensity dip in axial and radial directions near the node of the standing wave and can be used as an atom trap for blue detuning of the light. We simulated the behavior of two level atoms in this trap using the dressed state Monte-Carlo method and we show that it gives a good trapping when the residual intensity at the bottom of traps is small.

It has been shown that application of cubic gyrotropic crystals permits to extend functional opportunities of nonreciprocal elements on their base at the expense of receipt no one but two regions with essential value of phase nonreciprocity. It has been established that cubic centrally symmetric crystals with electroinduced anisotropy may be used while creating nonreciprocal elements which are controlled by electric field and polarization of the incident light. It has been grounded that anisotropic Bragg diffraction in biaxial crystals may be applied by elaboration of pure phase large-aperture nonreciprocal systems where it may be achieved the absolute absence of diffractional losses. It has been shown the opportunity of application of the double Bragg diffraction in uniaxial gyrotropic crystals (for example, paratellurite) near optic axis while creating pure reciprocal systems which are necessary for ring laser with mode synchronization.

An all-fiber, in-line Sagnac interferometer for magnetic field sensing is present. Magneto-optic effect in the sensing part produces a phase shift between orthogonally polarized light waves that travel back and forth in a fiber bus.

The paper presents an analysis of anisotropic grating in non-conical mounting. The grating is composed of the periodically alternating strips of anisotropic and isotropic material, so the relative permitivity tensor profile along the periodicity direction is piecewise-constant. The anisotropy is considered to be transversal and (in terms of magneto-optics) is induced by an external magnetic field in the direction perpendicular to the plane of incidence. The electromagnetic field in the grating region is expressed using Floquet modes and permitivity profile is expressed using Fourier expansion. Modal amplitudes are obtained from coupled-wave analysis performed in compact matrix form. The results are angular spectra of diffraction efficiencies for material and geometrical parameters. The numerical stability and convergence is discussed for every computed case.

The magneto-optical effects in reflection are often used for the investigation of the in-plane magnetization behavior in thin ferromagnetic films. The methods of the magneto-optical hysteresis loop measurements are presented for both magnetization components parallel and perpendicular to the external magnetic field. The influence of the longitudinal and the transverse magnetization on the reflection coefficients including the second order magneto-optical effects is presented. The formulas for the reflection coefficients and the magneto-optical angles are brought for the interface between an isotropic medium and a cubic magnetic crystal with the in-plane magnetization. The Yeh's 4 X 4 matrix formalism, based on eigen modes propagation in the anisotropic magneto-optical medium, is used for the calculation. The theory is introduced for the epitaxial Fe film evaporated on MgO substrate for the field along a magnetically hard axis. The second order effect of the transverse magnetization component superposes on the linear longitudinal Kerr effect. This undesirable second order effect can be attenuated by choosing the optimal magneto- optical quantity and the measurement geometry. On the other hand the normal incidence geometry is optimal for investigation of the second order magneto-optical effects, because the linear longitudinal and transverse Kerr effects disappear. The pure second order hysteresis loops are measured in this geometry. There is the reflection analogy of the Voigt or the Cotton-Mouton geometry.

The prism coupling in Kretschmann configuration for the study of ultrathin metallic films is discussed. An interpretation of the results for Ag and Fe thin films is given. The special attention is devoted the possibility to use this technique for the measurement of the linear and quadratic magneto-optical effects in thin film magnetic media.

The spectrum of light changes on its propagation through few-mode optical fibers due to the coherence-induced changes. They lead to the presence of modulated spectrum affected by intermodal dispersion when two completely spatially coherent modes of an optical fiber are included. This spectral modulation can be resolved even if the group optical path difference (OPD) between modes is greater than the source coherence length. In this contribution, the spectral changes of light occurring on its propagation through a two-mode optical fiber are analyzed both theoretically and experimentally. It has been confirmed experimentally, in accordance with theory, that the spectral modulations characterized by the wavelength-dependent periods of modulations can be resolved at the output of a two-mode optical fiber excited by low-coherence sources having different spectral widths. It has also been confirmed that the characteristics such as the unmodulated spectra and the wavelength dependences of both the visibilities of spectral fringes and the group OPDs between modes can be obtained. Moreover, it has been revealed theoretically that the configuration of a two-mode fiber, for which no spectral fringes are resoled, and a Michelson interferometer is suitable for the spectral analysis with a low-resolution spectrometer.

Unidirectional composite materials based on organic (polymer) fibers suffer from anisotropy of optical and thermophysical properties. The anisotropy was experimentally examined by using a He-Ne laser ((lambda) equals 632.8 nm) and measuring the degree and azimuth of optical polarization, and the indicatrix of reflected-light intensity. Samples with smooth, relief, and carbonized surfaces were investigated.

An experimental set-up for the measurement of light reflectance at wavelengths 0.63, 1.15, 3.39, and 10.6 um as well as of surface temperature of composite materials, based on polymer fibers, was developed, and reflectivity of composite samples heated in air and inert (argon) atmospheres was measured. Radiation with a flux density as high as up to 1000 W/cm square from a cw CO₂ laser was used for heating the samples under study.

Possible and already realized applications of porous silicon (PS) layers in silicon solar cell technology are overviewed. Four main directions are marked for PS incorporation: (1) heterojunction formation, (2) light trapping, (3) antireflection coating, and (4) surface passivation. Standard PS preparation technique is discussed and a new one is proposed, applicable for large area devices. Optical and electric parameters of PS layers, obtained at different electrochemical etching conditions, are presented. Experimental results of PS action are compared with calculations for light trapping and antireflection coating effects. Detailed study of possible passivation effect is given both for mono- and multicrystalline silicon solar cells. The obtained results show good perspectives for PS application in cheap and efficient silicon solar cell production.

Porous silicon (por-Si), which is being obtained by electrochemical etching of single crystalline silicon in electrolytes on the base of hydrofluoric acid, recently attracts the attention of specialists in photovoltaics even more due-to a number of its unique properties. However, at present, acceptable results are obtained only for the use of por-Si as antireflection coating for silicon solar cells (SC). In the present paper, previous experience of the use of por-Si in the silicon SC has been analyzed. On the base of examination of the por-Si properties, a number of new directions of improvement of photoconversion efficiency of structures with optimized layers of por-Si was envisaged. The results of numerical calculations carried confirm perspectiveness of use of por-Si for efficiency improvement for different types of silicon SC. These can be increase of their internal quantum output, expansion of operating spectral range toward ultraviolet and infrared spectrum range, decrease of losses of photogenerated power due-to the influence of bulk and surface recombination.

A theoretical evaluation of the photoelectric properties of a metal-insulator-semiconductor structure with induced inversion layer (MIS/IL) like the Al/tunnel SiO_x/p-Si structure by using of an external bias. The MIS/IL structure with a special inversion grid is considered. A back bias is applied between substrate and metal inversion grid. It investigate the effects of influence of external bias on the parameters of the MIS/IL structure and solar cells (SC) on said base. The functional dependence of the MIS/IL structure parameters and the electrical characteristics of MIS/IL photoelectric transmitters depends on back bias. Numerical results show that the external back bias to increase the photoconversion efficiency of SC on the MIS/IL base. Solar module is possible to creation. The auxiliary voltage from additional SC is applied to the inversion grid of several main SCs.