The resonance fluorescence of a harmonically trapped two- level ion is investigated including effects, which result from the quantized motion. The interaction of a cold trapped ion with a strong laser field is studied in two configurations in which dressed states structure become important, but heating of the ion is unessential.

The Faraday effect in potassium vapor pumped by nanosecond pulses of near resonant laser radiation is studied experimentally. The input radiation with linewidth 3 cm^-1 had a central frequency v_p equals 13055 cm^-1 which was 12 cm^-1 higher than 4S_1/2 - 4P_3/2 atomic transition frequency v₀ equals 13043 cm^-1. The strong spectral broadening of pump radiation allowed to observe the Faraday rotation at frequencies v_{+/- 1} equals v₀ +/- 2.5 cm^-1 located closer to the atomic resonance where the rotation was high. The decrease of Faraday rotation from 150 degree(s) to 20 degree(s) with the increase of the intensity of pump radiation from 2 (DOT) 10⁵ to 10⁷ W/cm² has been measured. The saturation of 4S_1/2 - 4P_3/2 transition is considered as a cause of suppression of Faraday rotation. The contributions of one photon resonance absorption, as well as of multiphoton processes, caused by more intense off resonant part of the broadened pump radiation (having frequency detuning 12 cm^-1), to saturation of resonant transition is discussed. The experimental results are compared with theoretical calculations performed.

The adiabatic following condition for the propagation of pulses in a three-level medium has been obtained. It is shown that the adiabatic criterion depends not only on the total Rabi frequency and pulse duration, but on the relationship between oscillator strengths of electric dipole transitions in an atom too. In particular, for (Lambda) - system if the oscillator strength for the pump transition is less or equal to that for the Stokes transition, the adiabatic following condition is preserved at arbitrary penetration depths. Otherwise it breaks down rather quickly with the distance of propagation.

The influence of the initial state preparation by an interaction with resonant traveling waves on the anomalous standing wave scattering of a two-level system with magnetic sublevels for arbitrary coherency (1) between the atomic sublevels and (2) between the polarizations of counterpropagating waves is discussed. The potential of the magnetic sublevels and light polarization in the formation of specific types of split initial momentum distributions is pointed out. It is found a new effect of narrowing of the interference fringes of the diffraction pattern taking place at particular case of the initial wave packet splitting involving two translation states, whose momenta differ by two photon momenta, corresponding to the same energy level. It is shown that this narrowing can be combined with the known asymmetric scattering.

The role of the initial state preparation of the coherent diffraction of atoms in the field of a standing wave is considered. It is shown that the time evolution of the atomic wave packet with a Gaussian initial momentum distribution of amplitudes, due to the constructive quantum- mechanical interference, occurs practically without transformation of the initial Gaussian form. Depending on the phases of the initial momentum distribution components, the increment of the atomic momentum can vary from the maximum possible amount (determined by the limiting speed of stimulated photon re-emission acts) to zero. Consequently, for Gaussian atoms the standing wave presents an effective mirror with controllable reflection angle.

We investigate the conquest of sideband laser cooling and heating due to weak broad-band noise for a harmonically trapped two-level ion. The two opposite processes from an equilibrium distribution in the ion's quantum state of motion, i.e., the ground state of motion is depopulated. As another consequence we find population inversion between different manifolds of the ion's combined quantum states of internal electronic structure and external motion. This effect only results from the quantized treatment of the ion's motion.

We investigate the marriage of two different optical nonlinearities, which allow us to control the operation regimes of an intracavity light generation. Two kinds of cascaded nonlinear optical schemes involved two- and three- Hopf bifurcations are presented.

In our paper we consider the behavior of both the Hermitian (observable) Stokes parameters of light and the phases difference that describes the polarization state of optical field. In general case we introduce two pairs of phase operators associated with the phase angles in 3D picture for the polarization Stokes parameters of light on the Poincare sphere. The special eight-port polarization interferometer is presented for simultaneous homodyne detection of both the Stokes parameters of light and the polarization phases and also of their fluctuations. It is shown that an anisotropic (spatio-periodically) Kerr-like nonlinear medium placed in the polarization interferometer can be used for generation and observation of the polarization-squeezed phase states of light.

We report on the observation of far field spatial distortions of a Bessel beam after passing through a Kerr liquid. A coaxial ring structure has been observed to occur at some threshold power. It consists of two closely spaced (1.5 - 3.5 mrad) sharp rings of comparable intensity and a diffuse inner ring of smaller intensity separated by 8 - 9 mrad. Evolution of the far field pattern with moving the sample along the propagation path of the Bessel beam shows strong dependence of beam distortions upon the position of the sample. The phenomenon is supposed to be due to nonlinearly induced phase aberrations resulting in the distortion of angular spectrum.

The problem of a two-level atom interacting with a nonmonochromatic radiation pulse is studied both with and without the resonant approximation. Using the time-dependent perturbation theory, the analytical expressions for transition probability of the atom are obtained. It is shown how, depending on the value of the field strength, the atom's excitation probability can be obtained with the needed accuracy. It is shown that the upper level population of the atom exhibits oscillations which are absent in the resonant approximation. It is shown that absorption probability and dipole moment spectrum are governed by interference between the spectral components of a non- monochromatic radiation involved in nonlinear interaction process. Spectral distribution symmetry with respect to the resonance frequency being destroyed, the atom can be excited even if there is no resonant component in the pulse spectrum.

A Saturable Absorber based on thin and dense Cs₂ + Rb₂ + K₂ molecular vapor mixture has been investigated. It is revealed that relaxation time of photobleaching effect in dense Cs₂ + Rb₂ + K₂ is decreased with the mixture density and achieves 280 ps. It is demonstrated experimentally that a train of 3 - 5 pulses with the pulse duration of approximately 300 ps is generated as a result of passive Q-switching of YAG:Nd³⁺ laser. Such experiments are possible to perform due to development of unique sapphire cell containing the mixture of molecular vapor. There are several advantages of the mixture usage as a Saturable Absorber for passive Q-switching of solid state lasers.

Various tetraphenylporphyrins (zinc, magnesium, free base) were excited to the upper electronic levels of the Soret band with the second harmonic of a mode-locked Ti-sapphire laser (394 nm). An up-conversion fluorescence set-up with the time resolution of 120 fs was used to measure the decay times of the S₂ fluorescence in conjunction with the risetime of the S₁ fluorescence. The depopulation of the excited electronic state S₂ was studied as a function of the metal ion and the solvent. The lifetimes of the electronic S₂ level, measured for ZnTPP and MgTPP in different solvents were (tau) equals 1.4 - 3.4 ps. The depopulation channel from S₂ to S₁ was studied by measuring simultaneously the decay of S₂ and the rise of S₁ fluorescence. The rate constant of the process can be correlated to the energy gap between the S₂ and S₁ levels, which depends on the nature of the metal ions and solvents. The rotational dynamics in the Soret band was also studied by measuring the anisotropy of S₂ ---> S₀ fluorescence. The anisotropy decay of S₂ fluorescence was found to be biexponential, with a fast component around 100 fs and a slow one (t >> 10 ps), attributed to the partial dephasing of the degenerate energy levels of the S₂ state and to rotational diffusion, respectively.

Based on the lithium vacancy defect structure model of non- stoichiometric lithium niobate, a correlation was found between the OH absorption band and dopant charge. In addition, the threshold concentration for suppressing the photorefractive effect in Sc doped lithium niobate was evaluated using phase-matching temperature measurements. It was also shown that hafnium can suppress the photorefractive effect. A criterion for searching for new nonphotorefractive dopants has been formulated. New possible candidates are suggested and crystals of some of them have been grown.

Optical transmission and scintillation light yields were measured in Ce³⁺-doped LuAlO₃ and (LuY)AlO₃ solid solution single crystals grown by the vertical Bridgman and Czochralski processes. Depending on the growth history, the crystals exhibit dissimilar transmission properties in the UV range. The as-grown color centers possibly responsible for poor transmission properties in the range of Ce³⁺ emission were characterized by exposing non-activated crystals to 1 Mrad of ⁶⁰Co gamma-rays. Radiation induced absorption in Ce³⁺-doped crystals is found to be higher in crystals with good initial transmission properties, while the crystals with high density of as-grown color centers are radiation hard. With time, partial slow-rate natural recovery from the damage was observed at room temperature in all studied crystals. Annealing at higher temperatures or optical bleaching contribute to recombination of gamma-ray induced color centers but affect inconsiderably the as-grown color centers.

A mechanism, explaining amplification of scintillations in mixed aluminates activated by cerium ions - (Y_1-xLu_x)AlO₃:Ce (0 <EQ x <EQ 1) is proposed. Quasichemical reactions of ions Ce³⁺ and Ce⁴⁺ with holes and electrons causing scintillations are considered. Is shown, that the intensity of scintillations increases with decrease of mean free paths of electrons and holes and that it is proportional to the parameter of the compositional disorder x (1-x). Also the mechanism of amplification of scintillations caused by transfer of excitation energy by excitons is considered.

In the present paper it is shown that one can present the porous semiconductor as a set of clusters of silicon atoms surrounded by SiO_x, as well as the single crystalline silicon substrate can be considered as an infinite cluster also. The formulae for the estimation of variable porosity of the material (including the value of critical porosity-- the percolation threshold, after which the characteristic phenomena are expected in porous silicon) and the forbidden bandgap value of clusters are suggested as functions of the sizes of nanocrystallites. A new fractal model of pore creation on the surface of a material is proposed also. The cases of semi-spherical, conical (V-groove dielectric isolation technology) and cylindrical (U-groove dielectric isolation technology) are considered. Formulae for the formed surface area S, material porosity p as a function of the depth and fractal dimension are obtained.

We present loss-energy spectra, Im ε ^-1Ω ), calculated by use Kramers- Kronig transformation to the far-infrared reflectivity spectra of the superconducting YBa₂Cu₃O_7-x, Bi₄Sr₄CaCu₃O_14+x, Bi₂Sr₂CaCu₂O_8+x a-axis oriented textures in a frequency range 50 - 700 cm^-1 at temperatures 20 - 300 K, focusing on the phonon properties in the undoped structures. Fano-like antiresonance minima near 300 cm^-1 has been observed in a-axis oriented textures well below T_c and analyzed by Fano configuration interaction theory as result of interference between the B_2u (B_1g) plane- oxygen mode and low-energy charge continua that arises from electronic excitations on the Fermi surface.

The geometric peculiarities of the rough surface of a metal are revealed, when due to the essential shortening of the wavelength of the surface polariton excited by the light localization in a very small region of a space take place.

Monocrystalline c-axis oriented thin films of PbTiO₃ with various hole concentration were prepared by Cu doping with 0.1, 0.5, 1.0 mas.% and substituting Zr for Ti (Zr:Ti equals 52:48). We report concentration-dependent far- and mid- infrared reflectivity spectra of these compounds focusing on the electronic properties. Optical functions (ε ₁, ε ₂, σ , -Im ε ^-1) have been analyzed by Kramers-Kronig transformation to reflectivity spectra measured in a frequency range of 200 - 10000 cm^-1 at room temperature. Conductivity spectra show a complete semiconducting dependence that can be analyzed by Drude-Lorentz model and in the terms of dynamic interaction, which leads to a frequency dependent scattering rate and enhanced low-frequency carrier mass 0.5 mas.% Cu in PbTiO₃ decreases effective mass from 3.5 to 1.5 near 200 cm^-1 and increases relaxation time as compared with the undoped sample.

A short description of optical systems of space astrophysical observatories Orion 1 and Orion 2 is presented. With the help of these observatory-spectrographs, the short wavelength spectrograms, up to 2000 angstroms, of individual stars have been obtained. A concise resume of main scientific results derived from these spectrograms are presented as well.

A short description of the project CHROMOS, a space astrophysical observatory, consisting by three telescopes- spectrographs and one telescope-astrograph, all with working angle of 5 degree in diameter and wavelength region 2000 - 3000 angstroms. The optical schemes of all four telescopes are presented together with their optical and geometrical parameters.

An optical system of three-cannal telescope-spectrometer is proposed for the registration of the spectra of individual stars in the extreme short wavelength region, shorter 500 A up to 100 A (project VESTAL). The calculated optical parameters of both components of main telescope, two parabolic mirrors with entrance diameter of 1200 mm and three spectrometers of Wadsworth system, are presented as well.

The quantitative analysis of the mechanism of S- and N-type negative differential conductivity (NDC) of electrons in low-temperature plasma due to the electron-electron interaction (EEI) is presented. It is shown that EEI along with NDC of electrons can initiate the generation of high- frequency domains moving with velocities of the order drift velocity of electrons accompanied in some cases with the discontinuous constriction of positive columns of glow discharges. The estimations show that EEI can be displayed in a large number of gases and gas mixtures; comparisons with experiments and numerous simulations confirm the validity of the proposed theory. The use of powerful spectroscopic diagnostic methods is necessary for the tracing of dynamics excited species needed for elaboration of self-consistent description of NDC of electrons.

Quantitative analysis of instabilities in microwave low- temperature plasma is carried out by taking into account electron-electron interactions. In particular, it was obtained that S-type negative differential conductivity (NDC) of electrons can be observed in microwave plasma, if this plasma in dc field displays N-type NDC of electrons (both effects have to be compared at the same value of mean electron energy). The conditions for observation of negative radiation temperature are estimated. Radiation temperature in gas mixture is presented as simple function of plasma macroscopic parameters in single gases composing a given mixture.

Metal targets covered by micrometer layers of metal- phthalocyanines or fullerenes are studied here. An increase in XUV yield due to the optimized absorption of the laser field is reported. Effects of high-temperature plasma rapid expansion (velocity about 10⁶ cm/s) were observed. Moderate power nanosecond and picosecond neodymium lasers are used to produce an incident intensity of 10¹¹ to 10¹³ W/cm² on the targets. The plasma electron density was measured by fitting observed spectral profiles to the theoretical profiles. Collisional, Doppler, and Stark broadening mechanisms were considered in the calculations. Our measurement technique permits us to determine the electron density and temperature dependence on distances from the target surface from 1 mm (where N_e approximately equals 10¹⁸ cm^-3 and T_e approximately equals 14 eV are measured for aluminum plasma) up to approximately 5 mm (where N_e <EQ 10¹⁷ cm^-3). Electron temperature was measured by comparing intensities of spectral lines, belonging to the ions having a different degree of ionization. Preliminary experiments show that conversion efficiency for molecular coated targets is greater by a factor of approximately 1.5 than measured from bulk solid metal targets.

Soft X-ray radiation from krypton and nitrogen clusters in a supersonic gas jet is studied here. Isolated lines of He- like nitrogen ions in the 1.5 to 3.0 nm wavelengths region and of 7 to 13-charged ions of krypton in the 1.5 to 20 nm region are observed using to 4 to 6 keV electron beam excitation with 50 to 75 mA beam current. The obtained spectra are investigated depending the gas jet flow and excitation parameters.

Supercritical CO₂ can induce crystallization of amorphous polymers. Molecular level insight into the microstructures of CO₂-processed polymers is needed to form a basis for utilization and optimization of supercritical fluid processing of polymeric materials. Spectroscopy is an economic tool to probe interactions at a molecular level. This understanding will help engineers to utilize molecular level information for improving macroscopic properties of polymeric materials by supercritical fluid processing. FT-IR spectroscopy has been applied to elucidate the morphology and microstructure of polymers processed with supercritical CO₂. FTIR spectra of syndiotactic polystyrene show an increased degree of crystallinity after being subjected to scCO₂. The various crystalline forms induced by CO₂ in syndiotactic polystyrene were characterized via FTIR spectra. FTIR spectroscopy has been also used to measure the kinetics of CO₂-induced crystallization in these polymers.

Comparative study has been performed of the influence of pumping by two separated wavelengths λ equals 520.6 and λ equals 578.2 nm from a copper vapor laser on the output characteristics of a Al₂O₃:Ti³⁺ laser. It is shown that the pumping by the long-wave spectral component of the copper vapor radiation is comparable in efficiency with pumping at the wavelength for the shortwave part of the Al₂O₃:Ti³⁺ laser generation range. The differential efficiency 26% in the center of the amplification line of the Al₂O₃:Ti³⁺ laser at the wavelength 770 nm is obtained.

We report highly efficient cascade tripling of 1.32 micrometers Nd:YAG laser emission using combination of LiIO₃ and KTP crystals. The generation of 0.44 micrometers radiation in KTP has been shown to occur at the purely noncritical phase-matching condition at slightly elevated temperature. Conversion efficiency of third harmonic generation in relation to second harmonic energy was approximately 60% in 4 mm long KTP crystal. The temperature and angular characteristics of conversion are presented.

We observe the forming of modulation pulses, by registration the optical pulses modulated in the time by photomultiplier which works in a photons count (PC) regime. The separate PC pulses are registered in the case of low light intensity. Pulse of modulation is formed if the intensity increases. It is shown, that the minimal registrative duration of the pulse is determined by one photo-electron (OPE) pulse. It imposes limitation on the possibility of signal registration. In the space language, it leads to minimal possible size of the picture spot, which is limited by the size of photosensitive grain of photoplate. The resolution of both a optical communication on a long distances or by the registration of supershort pulses will be limited also by the duration of OPE pulses.