We present results of the research and development of CW fiber lasers with reflectors based on multimode fiber Bragg gratings. Considered laser schemes used cladding pumped active fibers as an active medium. We have shown that multimode fiber gratings written in the graded index multimode fiber can be used to form the cavity of different types of the fiber lasers. In particularly we have fabricated single mode and multimode lasers based on all-silica and polymer coated double-clad active fibers. The realized lasers were based on Yb-doped fibers having an emission band between 0.98 and 1.1 μm, and based on Er-doped fiber with an emission wavelength near 1600 μm.

A1GaAs/GaAs quantum-well diode laser (824 nm) with the short external cavity was used for water diagnostics in the pumped out gas cell. The laser provided the 63 GHz continuous tuning of the optical frequency by the scanning of a pump current and a spectral linewidth of oscillation was less than 0,2 GHz. The experimentally obtained dependence of a second derivative amplitude on the vapour pressure coincides well with the calculated curve in the range of 0,4-20 Torr. The change of output signal close to linear was recorded at a pressure in the sample gas cell less than 5 Ton. The minimum concentration of H20, which is still measured by the diode laser sensor is estimated at a level 1,5x10¹⁵ molecule/cm³.

A new effect of light localization in nonlinear layers of photonic crystal is predicted. It is shown that during the initial pulse propagation through the nonlinear medium an ultra-short high-intensity solitons, which are reflected from the boundaries of the linear and nonlinear layers as a whole, are formed. Hence, the soliton sub-pulses are captured by the nonlinear layer of the photonic crystal. Soliton interaction is discussed as well. Computer simulation based on a new approach for this class ofproblems is proposed by the authors.

The TLM method is used to characterise microwave parameters of two different types of the modulator, namely the lumped and the travelling wave modulator. The modulators are compared in terms of their characteristic impedance, effective refractive indices, capacitance and microwave loss. Furthermore, the impact of the electrode size, semiconductor mesa and finite metal conductivity on the microwave characteristics of modulators is investigated and compared for two different types of modulators.

The Green functions and corresponding integral and integro-differential equations for periodic structures are introduced. Some results based on this approach for 2D and 3D photonic crystals are presented. We consider the simplest photonic crystals, but the method is applicable to arbitrary shaped structure and may use the volumetric finite elements. The solutions of integral and integro-differential volumetric and combined surface-volumetric equations are considered and discussed. Also the method which reduces the kernel singularity is proposed and considered. The method is based on the transferring of differential operators from the kernel to the unknown functions under the integral. The dispersion equations is based on the variation formulation for integral and integro-differential equations and have been used to obtain the permittivity and permeability tensors for photonic ciystal's equivalent complex media.

In the present paper the excitation of cylindrical structures (waveguide and resonator) by helix and axial electric currents have been considered using exact electromagnetic approach. In the solution of the problem the coupling of resonator with input and output coaxial lines and possible excitation by elecon beam and by input signal are considered. Beam current is supposed to be given and problem is linear and time-independent. The results can be used for processes simulation in the systems with helical slow-wave structures, such as TWT. This approach can be applied also for investigation of wave propagation in photonic crystals with small helical inclusions. Using such artificial environment allows to well simulate environment with large permittivity.

A new variant of localized function method is used for the simulation of beam propagation in photomc crystal fiber. The method based on the field approximation in terms of orthogonal Laguerre-Gaussian functions. Effect of the gain saturation on the formation of the beam structure in nonlinear photonic crystal fiber is investigated. For few-mode fiber the resulting beam structure depends strongly from initial conditions. The endlessly single-mode photonic crystal fiber operates at fundamental mode for a wide active region and large gain.

The decomposition of the beam on a set of orthogonal Laguerre-Gaussian functions is applied for modehng pulse dynamics in few-mode microstructure fiber. In the scalar approach the nonlinear propagation of ferntosecond pulses in the anomalous dispersion region of microstructure fiber investigated. The simulation demonstrates the generation of dispersive waves in high-order waveguide modes.

Electromagnetic wave diffraction on a cylindrical dielectric grating is considered. The problem is reduced to integral equation. Logarithm singularity of the integral equation kernel is extracted in explicit form that allows to solve integral equation changing integral by the high-precision quadrature formulae. Such analytical transformations result in high convergence of the algorithm. Angular and spectral dependencies of E-polarized wave through the dielectric grating are analyzed for different kinds of polygonal cross-section.

The Jaynes-Cummings model (JCM) of two-level atom interacting with the photon mode in ideal cavity plays an essential role in modern quantum optics. In previous papers an exact form of density matrix of the JCM with photons dissipation was found. In this article it is considered a partial case of cavity with zero temperature and obtained an exact expression for photon spectra and spectra of the mean number of photons in a cavity.

In this article the possibilities of different laser beams regeneration after an obstacle that can be the microparticle, trapped by the beam, are examined. The comparative analysis of regeneration properties of the Bessel beams, the Gauss-Laguerre modes and other beams, containing angular harmonics, is made. The forming of such beams has the maximum effectiveness with the help of phase diffractive optical elements. The experimental results of the Bessel beams regeneration, including those of none-zero order, are presented.

Semiclassical theory of cooperative Rayleigh scattering of laser light from Bose-Einstein condensate of dilute gas is considered. The different versions for the process initiation are analyzed.

The collective spontaneous radiation of the macroscopic system of V-type three-level atoms interacting with quantum electromagnetic field and coherent pumping field has been investigated on the basis of the Bogolubov's method of the elimination ofthe boson variables. The possibility of the subradiant and superradiant regimes in dependence of the pumping area has been established.

We consider integral transforms that can describe ideal imaging optical systems with circular impulse response. The integral transform, referred to as the Circular Radon transform (CRT), is considered as an average taken along all circumferences offixed radius on the plane. The CRT can be optically realized using a Fourier correlator with amplitude filter, with its transmittance function being proportional to the Bessel function of zero order. Also, a mesooptics transform (MT) is considered that can be optically re*alized using a Fourier correlator with axicon in the spatial-frequency plane. An ability of applying the CRT to realize traditional Radon transform optically has been tested.

We consider a fast iterative algorithm for calculating the monochromatic electromagnetic wave diffraction by dielectric microobjects of near-wavelength size. The results of numerical simulation of diffraction of the TE- and TMwaves are compared with the exact analytical solution. The algorithm is used for calculating Umov-Poynting vector and the pressure force exerted by the non-paraxial cylindrical Gaussian wave on a circular micro-cylinder.

Discrete algorithms for symbolic computation of topological phases and observables in optical interferometric systems are presented and illustrated using a set of test models. The calculation of the parameters of a birefringent plate that can be measured by means of Mach-Zehnder interferometer is implemented in terms of Maple and Mathematica. Near-field test models of the systems, that possess both geometrical and dynamical phases in the far-field region, are constructed beyond the the bounds of the ray approximation. These models imply a set of discrete sources with variable parameters and make use of the appropriate set of separable potentials.

An economy method of numerical solving the partial isospectral 2D boundary problem in self-consistent basis is elaborated. An efficiency of the method is shown for an integrable system described by a generalized Henon-Heiles Hamiltonian depended on two real-values parameters.

With the use of IR spectroscopy methods (experiment and theory), we investigated the features of structure and intermolecular interaction in the homological rows of4'-n-alkyl-4-cyanobiphenyls (hereafter nCB, where n is the number of carbon atoms in alkyl radical (AR)). We measured the JR absorbance spectra of the samples of NCB (n=2, 4, 5, 8, 9) in the 400-4000 cm1 frequency region in the 26-100°C temperature range for solid crystal (SC), liquid crystal (LC), and isotropic liquid (IL). We performed theoretical simulation of the JR spectra of the nCB molecules (n=1...9) with taking into account their conformational mobility. We performed the analysis of the measured spectra with taking into account available X-ray data concerning intermolecular interaction in these substances. On the basis of theoretical modeling, we presented the interpretation of the existing data. We found conformational inhomogeneity of the samples in various phase states and estimated the influence of intermolecular interaction as a structure-forming factor.

The results of the structure features and intermolecular interaction investigations in long-chain aliphatic compounds (LCAC) by JR spectroscopy (experiment, the theory), differential thermal analysis, polarizing microscopy, and X-ray methods have been generalized. The objects for the researches have been the carboxylic acids derivatives (alkyl- and alkyloxybenzoic, alkylcyclohexanecarboxylic and their completely or partially fluoroalkyl substituted), 4-n-alkyl-4'- cyanobiphenyls, 4-n-alkiloxy-4' -cyanobiphenyls n-n' -butyloxybenzoate of cholesterol. The results of investigations have been proved by the data of the infra-red spectrum LCAC modeling taking into consideration conformational mobility of molecules and intermolecular specific interaction (H-bond). Both factors become apparent in JR spectra and determine LCAC structure features. It is established, that the conformational mobility of molecules.

The problem of investigation of fine structure energy levels of bound states is considered. The comparison analysis of high order logarithmic corrections is described. New logarithmic corrections about α⁶βlnβ obtained.

The analysis of nitrobenzene and nitropyridines vibrational spectra has been performed for free molecule and in water, ethanol and benzene solution using DFT/B3LYP method with 6-31G*(**) basis set. Solvent influence on the nitrobenzene characteristical spectral parameters behavior was found. Assignment for vibrations of nitropyridines is given.

The crystal structure of 2-biphenylmethanol has been studied by X-ray crystallography at room temperature and its JR transmittance spectra have been measured in the wide frequency region 400-4000 cm^-1. The structure, energy, electrooptical parameters, frequencies and intensities in the IR spectra for the free molecules of 2-biphenylmethanol, methanol, and tetramer of hydrogen-bonded methanol molecules have been calculated at the B3LYP level of the density functional theory with the 6-3 1G* basis set. Based on analysis of the obtained results the interpretation of the JR spectra for room temperature was given and estimation of the hydrogen bonds energy has been done.

Fluorescence techniques of recording EXAFS spectra are considered: XEOL and fluorescence EXAFS. The main causes of spectra distortions induced by both experiment conditions and mechanisms of luminescence's appearance under the action of synchrotron radiation. The algorithms of correction of experimental spectra to compensate for distortions are considered. By the example of alkali-halide crystals, it is demonstrated that, as the spectrum is recorded, radiationinduced transformations of the structure can occur in the sample. These transformations are not brought out in EXAFS spectra, but are detected by the XEOL method.

Spectral characteristics of NaC1-Ca,In crystals were investigated. Calcium was used as a coactivator. Changes in the absorption, luminescence and excitation spectra of the crystals as a result of doping with Ca and as a result of the action of following factors: X-ray radiation, heating, storage of a crystal have been analyzed. Effects of the coactivator on the efficiency of formation of luminescence centers in the crystals are discussed. Suggestions about the structure of luminescence centres in the crystals were made.

Computer simulation of aqueous solutions of some biological active and inactive compounds has been carried out. Molecular dynamics method and TIP3P potential were used. The parameters of hydrogen bonds net were calculated by using the developed computer program. The simulation showed that relatively large clusters of water molecules appeared and the average number of hydrogen bonds decreased in the aqueous solutions of biological active compounds. It points to the fact that these compounds may induce the phase k-transition in the surrounding water. Molecular mechanisms ofthese effects are discussed.

The influence ofthe strong magnetic field on the spontaneous recombination ofthe antihydrogen in cold positron-antiproton plasma is studied. The consideration is based on the analysis of the classical trajectories. The calculation of the relative cross section ofthe positron capture is carried out using the Monte-Carlo method and then the result is compared with the one in the situation when the magnetic field is absent. It is expected that since the trajectory of the positron in the magnetic and Coulomb fields is rather complicated, and the free positron passes the nucleus many times, the probability of the radiative capture will be greater than in the zero magnetic field, when the positron having the positive energy passes the nucleus only once. However, our calculations showed that the magnetic field does not affect significantly the radiative recombination rate within the approximations used. The comparison with the experimental study of the recombination of matched beams of electrons and filly ionized carbon nuclei in the magnetic field revealed fourfold underestimation of the relative recombination cross section, which is probably a manifestation ofessentially quantum effects.

Use ofthe comma is the most problematic place ofthe English language for the Russian users. Some rules on the comma usage do not work, others are incorrectly formulated. The list of cases of use amounts from a dozen to thirty, and intuition is not the one to rely on. The material for the case analysis has been taken from the most recent grammar manuals compiled by the English-speaking linguists.

It is essential that our audience be attentive during lecture, report or another presentation on physics. Therefore we have to take care of both speech and visual communication with audience. Three important aspects of successful visual aids use are singled out in this paper. The main idea is that physicists could appreciably increase efficiency of their presentations by use of these simple principles of presentation art. Recommendations offered are results of special literature research, author' s observations and experience of communication with skilled masters of presentations.

In the present paper photonic crystal fiber properties were studied. Group velocity dispersion and nonlinearity factor of the fiber were obtained. Pulse parameters, needed for fundamental-mode or high-index-mode solitons to form such fibers, were estimated.