The spectral characteristics and stability of a frequency of intermode beats of a femtosecond self-mode-locked Ti:S laser are investigated. An active method is used to obtain high stability. The frequency stability of intermode beats not lower than 2.5 (DOT) 10^-13 rms in 100 s is achieved. Possible applications of the setup, such as measurement of large frequency intervals in the optical range, creation of optical frequency synthesizers, etc., are proposed. The physical properties for the creation of an optical clock of a new type using highly stable femtosecond Ti:S laser are considered.

In this paper we discuss the quantum optical element XOR (XOR-gate) on the basis of switching of macroscopic polarization states in Mach-Zehnder interferometer for single-photon pulses. It is shown that the state at the output of the optical system has the Schrodinger cat macroscopic superposition properties in polarization characteristics.

We developed a laser system at 457 nm based on a CW ring Ti:Sap laser and an enhanced cavity SHG in LBO and KN crystals with linewidth < 30 KHz for interferometry experiments with Mg atomic beams. For laser cooling and deflection of a Mg beam, a laser system at 285 nm based on a ring R6G CW dye laser and SHG in BBO nonlinear crystal has been realized. The results of Mg interferometry experiments in four-beam Borde' geometry and the results of Zeeman cooling experiments in a transverse magnetic field are presented. Zero order interference fringes corresponding to the recoil doublet with the resolution of approximately 30 KHz were detected. A Mg beam with a flux of approximately 10¹¹ atoms/s, the mean velocity of approximately 200 m/s, and the width of velocity distribution of approximately 50 m/s (FWHM) have been obtained.

The local field correction in semiclassical model of superluminescence is presented for short and pencil-like samples. We propose a new experimental technique for stability measurements based on Fourier spectroscopy of laser pulses interacting with dense self-chirped resonant media having many atoms within a cubic wavelength an d theoretical model of the two-photon Fourier spectroscopy of Cs.

Stabilizing quantum algorithms against external perturbations and preserving quantum coherence are main challenges in the area of quantum information processing. In this contribution main ideas underlying a new class of recently proposed embedded error-correcting quantum codes are discussed. These detected-jump correcting quantum codes are capable of stabilizing distinguishable qubits against spontaneous decay provided these decay processes originate from couplings to statistically independent reservoirs. Exploiting the classical information about which qubit has been affected by the environment these embedded quantum codes minimize the number of required control measurements and recovery operations as well as redundancy. Their stabilizing properties are exemplified by applying them to Grover's quantum search algorithm.

The problem of formation of macroscopic (mesoscopic) coherent superposition of polarization states for boson-like systems are discussed for the first time. The quantum interference of two (and/or more) coherent states in boson systems results in nonclassical polarization states being described by us by different way: the Wigner quasi- distribution function, boson statistics and entropy of quantum states. The phase transition from classical to quantum state of the system in such a `frozen' mesoscopic system (quantum dots) is obtained. The behavior of the Wigner function under the phase transitino demonstrates the fractal-like structure. The application of considered coherent superposition of quantum states and induced phase transition in mesoscopic systems to construction of the quantum logical gates for quantum computation are discussed as well.

The coherent information concept is used to analyze a variety of simple quantum systems. Coherent information was calculated for the information decay in a two-level atom in the presence of an external resonant field, for the information exchange between two coupled two-level atoms, and for the information transfer from a two-level atom to another atom and to a photon field. The coherent information is shown to be equal to zero for all full-measurement procedures, but it completely retains its original value for quantum duplication. Transmission of information from one open subsystem to another one in the entire closed system is analyzed to learn quantum information about the forbidden atomic transition via a dipole active transition of the same atom. It is argued that coherent information can be used effectively to quantify the information channels in physical systems where quantum coherence plays an important role.

Physical-chemical and optical properties of glassy system Ga-Ge-S, doped with Nd³⁺, Er³⁺ were treated from viewpoints of differential-temperature analysis, Raman and luminescence spectroscopy. Strong correlation between network structure and luminescence efficiency of Ga-Ge-S:Nd, Er system is established. Increase of Ga₂S₃ contents in Ga-Ge-S:Nd, Er system leads to forming of ternary structure units and enhances luminescence efficiency.

The paper pursues an experimental investigation on solid- phase destruction of thin surface silicon layer (h approximately equals 10^-4 cm) in vacuum, related to accumulation of dislocations under periodic action of short pulses. It has been concluded that the destruction of sample surface will be governed by competition of processes of dislocation growth and relaxation. It has been shown that the destruction of surface is caused by the requisite number N_c of laser pulses. The plots of N_c against power density and pulse repetition period have been constructed.

The experimental studying of laser-induced hydrodynamic phenomena has been carried out by the system on base of laser brightness amplifier. The surface waves were registered and their parameters were determined. The form of free surface of melted by the laser radiation material was determined. New results of the field to study the laser- induced dynamic processes on the substance surface by the fractal geometry approach are presented.

The experimental studying and mathematical modeling of laser-induced hydrodynamic phenomena has been carried out. The mathematical modeling of waves on surface of melted material is realized for case of pressure of return vapor presence. The form of free surface of melted material under the laser radiation action were determined.

We present numerical calculations on the field distribution in the focus of an optical system with high numerical aperture. It is shown that a radially polarized doughnut mode fits the symmetry of the optical system and focuses down to spot sizes significantly smaller as compared to the case of linear polarization. An experimental setup to generate a radially polarized beam is presented along with a setup which is based on the knife edge method and tomographic reconstruction to measure the 3D intensity distribution in the focal region.

The multimode instability commonly observed in erbium-doped fiber lasers in shown through systematic experiments to be of the Risken-Nummedal-Graham-Haken instability type. The onset of instability occurs with a well-defined threshold which scales with cavity loss in the expected way. Before, this type of laser instability has eluded experimental demonstration for 30 years.

In this paper, we elucidate the role of the rotational degree of freedom for the process of laser distillation of enantiomers from a racemic isotropic solution for any possible laser scenario. It is shown that the laser distillation scenario suggested by Shapiro et al., which is based on coherent control, does not work for the achiral synthesis from a racemic isotropic solution. This is due to the fact that rotational degrees of freedom of enantiomers constituting the solution are homogeneously distributed over the Euler angles and averaging over this distribution cancels the effect. A modified scenario is suggested, which works for the case of isotropic racemic solution. A detailed analysis of this scenario shows its efficacy for the preferable synthesis of enantiomers of required handedness.

The stretching mode of OH-groups with proton donor function of an alcohol associating to open hydrogen-bonded dimers is investigated in the liquid phase. Spectral holes with frequency spacing of approximately equals 35 cm^-1 in the fundamental OH-transition and of approximately equals 45 cm^-1 in the excited state-absorption are determined. This gives strong evidence for combination tones with the bending vibration of the hydrogen bridge bond governing the dynamics and the shape of the proton donor OH-stretching band. The combination modes display additional relaxation channels for the excited OH-stretching mode resulting in a lifetime shortening from 8 ps (monomer) down to 3.6 ps (proton donor, 260 K).

Diagnostics of gas mixtures with fluctuating temperature, density and concentration composition requires simultaneous detection of spectra of all species of a mixture with subsequent its joint treatment. Strategy of processing of experimental data, obtained at diagnostics by methods of a spectroscopy of Coherent Anti-Stokes Raman Scattering, is considered. An experimental approach to a performance of density numbers measurements in three-component mixture of O₂, H₂, H₂O in a flame of oxygen-hydrogen burner is presented.

The paper presents the results of a study on spectral composition of non-thermal glow from tungsten surface (mechanoluminescence--ML), that is initiated by thermal deformations under laser pulse action. Spectral relationships of glow intensity have been obtained. It has been shown that ML of tungsten exhibits a wide spectrum and is present throughout the spectral range under study ((lambda) equals 460 - 760 nm).

A highly sensitive photoinduced polarimetry method was applied to probe optical anisotropy of the photoexcited states in non-oriented films of nano-polyacetylene. The photoinduced absorption anisotropy was observed in both cw and transient polarization experiments. The photoinduced dichroism parameter of the nano-polyacetylene films, (mu) equals (forula available in paper) was measured on the sub-nanosecond time scale ((mu) approximately equals 1) and on the millisecond time scale ((mu) approximately equals (formula available in paper) are the absorption indexes of the linear polarized probe polarized along and across the linear polarized pump, correspondingly. We discuss delocalization of (pi) electrons in the photoexcited states of trans-nano-polyacetylene chains.

The main up-conversion mechanisms of the anti-Stokes luminescence of rare-earth (TR³⁺) ions were considered, such as summation of photon energy through energy transfers, successive absorption of photons, cooperative sensitization, and cooperative luminescence. The analysis of the specific features of the up-conversion mechanisms was performed on the micro- and macroscopic levels. On the basis of the survey of literature data on the given themes, the general systematization of the mechanisms of up-conversion phenomena was obtained. The rate equations describing the populations of energy levels of TR³⁺ ions for the cases of system with activator and sensitizer and system without sensitizer are given in the general form. The photon avalanche effect is considered.

We demonstrate a simple and effective method of a multiple- frequency operation of diode laser by using the direct RF modulation of injection current. A substantial fraction of the total laser power (up to 40%) was obtained in a single side band at frequency range from 2.5 GHz to 4 GHz with microwave power less than 26 mW. We have found simple explanation of the high efficiency of modulation of the laser radiation spectrum based on resonant excitation of a relaxation oscillation.