For calculation of eigenmodes of microstructure fibers the beam approximation by a set of orthogonal Laguerre-Gaussian functions is proposed. For structures with hexagonal lattices this method allows to reduce the number of governed functions. For simulation a beam dynamics in microstructured fibers is proposed to apply a wide-angle scheme. In conjunction with approximation of the beam structure by Laguerre-Gaussian functions this method provide sufficiently fast and accurate numerical scheme.

The experimental substantiation of the theoretical thesis, that excitation of the laser radiation fluctuations, due to instability of an electrooptical feedback circuit, occurs on intermodal (roundtrip) frequencies, established earlier, is received, i.e. accompanied by transition of the laser generation in a synchronized modes regime. This is the synchronization modes of active type because electrooptical Pockels lock was used for the generation handling in the experiment. It became easily to obtain such phenomenon due to use of a broadband feedback circuit which is formed by a broadband photodetector and specially designed for a feedback circuit broadband amplifier. It is shown, that for effective transition to a synchronized modes regime with the attraction of the non-linear filters is also necessary. Reduced train of ultrashort pulses received for a case of positive feedback allows to hope, that effective lengthening will be possible in a case of negative feedback that is important for medical applications, for example.

Polaritonic excitations in a layer with strong excitonic response are theoretically studied. The dielectric function of the layer is assumed in the Lorentzian form with only one excitonic pole taken into account. The dispersion as well as optical absorption spectra of polaritonic excitations in such a layer are calculated. Both cases of symmetric and asymmetric dielectric environment of the excitonic layer are considered. Special attention is paid to so-called slow radiative polaritons excited in the total reflection regime. The problem of the impact of the higher polariton modes on optical spectra of the excitonic layer is addressed for the first time.

The Green functions and corresponding integral and integral-differential equations for periodic structures are introduced. Some results based on this approach for 1D, 2D, and 3D photonic crystals are presented.

An equation describing the generation of reflected radiation during the propagation of high-intensity extremely short pulses in a nonlinear optical waveguide is derived. The phenomena taking place during the strong self-inducted changes of the temporal structure of the forward wave are studied. It is shown that the duration of the backward pulse is much greater than the duration of the forward pulse and that the main part of the energy of the backward wave is carried by lower frequencies than the central frequency of the forward wave.

The numerical model of stimulated Raman scattering (SRS) taking into account spatial dynamics of amplitude-phase characteristics and consisting of non-linear partial parabolic differential equations is developed. A finite-difference numerical method was used to solve these equations. Results of simulation are in good agreement with experimental data.

This work is devoted to studying the phenomenon of refraction at an interface of a two-dimensional photonic crystal (PC) and a uniform dielectric. Refraction laws were obtained by means of isofrequency method. Different types of refraction depending on the incident wave vector, outer medium and PC refraction indexes and mutual orientation of the interface and PC symmetry axis were observed.

We consider peculiarities of coherent population trapping (CPT) effect on magnetic sublevels of fine structure levels for Thallium (TI) atoms. The system of levels taken into account consists of eight levels. By considering spontaneous decay onto the levels of thermostat we have found the solutions of Schroedinger equation in resonant approximation and so we have found the populations of magnetic sublevels. We have considered different geometries of experiment. Among them there are the cases for which the polarization vectors of both components of radiation fields are parallel to each other and parallel or perpendicular to magnetic field, polarization vectors are perpendicular to each other (one of them is parallel to magnetic field). Also the orientation of magnetic field may be parallel or perpendicular to wave vector of radiation field. Also we have considered different initial populations of magnetic sublevels. In contrary to trivial initial populations of sublevels of the ground state of an atom we have considered the initial population of another metastable fine structure level of TI atom. This situation can take place for atomic photofragments produced in the photodissotiation of diatomic molecules.

The possibility of the observation of the vacuum electron-positron pair creation under action of the optical laser field is discussed. We employ the quantum kinetic equation with the source term describing the vacuum pair production. The approximation of the homogeneous electric field, weak in comparison with the critical value E_cr = 10¹⁶V/cm, is used. The electron-positron plasma density changes periodically with a double field frequency. The mean density value is proportional to the square field intensity and does not depend on the frequency. That allows to expect that the possibility to observe the vacuum creation effect by means of the existing optical lasers is not less than one for the planned X-ray free electron lasers.

A special class of separable potentials in the momentum space is proposed which is equivalent to 3D δ-functions in the configuration space. These potentials allow generation of a large number of exact solutions of time-dependent and time-independent Helmgoltz (Schroedinger) equations. It is shown numerically that in the 1D case δ-functions effectively approach the continuous potentials via a convergent algorithm.

The effect of speckle displacement in the region of the image of a rotating plane specimen revealed earlier is applied to studying rotation of objects under deformation. In the experiment a cylindric specimen is tensioned up to fracture. The total rotation of the surface of a specimen under plastic deformation, which is measured by speckle displacement, and the slope of the surface measured by a photograph of the fractured specimen are shown to coincide to within the measurement errors. The displacements are shown to appear in plastic deformation, to be symmetric about the center of the image of the working part of the specimen and to have opposite directions.

A dynamic speckle-interferometry method based on continuous monitoring of speckle-fields reflected from two objects under deformation is described. The aim of the paper is to verify the correctness of the formula relating the vector of relative displacement of body areas to the order of interference at the observation point. The formula coincides with a similar formula found in holographic interferometry. The lines of interference periods found on the image by dynamic interferometry are shown to agree well with the lines of equal interference periods obtained under identical conditions by holographic and correlation interferometry.

Exact analytical expression for the density matrix of atom + field system is obtained taking into account of the photons relaxation and frequency detuning (Jaynes-Cummings model with m-quantum transitions and dissipation). The photon mean number, atom population inversion and Fano Q - factor depending on initial states of the field and parameters of the one-atom maser are investigated.

High accuracy splitting algorithms based on the unitary approximations of the evolution operator for the time-dependent Schrodinger equation (TDSE) with a train of laser pulses are developed. The efficiency of the algorithms is shown using typical examples of a hydrogen atom affected by a train of laser pulses in the dipole approximation and an additional constant magnetic field. The stabilization effects are discussed.

The dynamics of detuned two-level Jaynes-Cummings model with multiphoton transitions in the finite Q-cavity has been considered. The time evolution of the mean photon number and atomic populations has been investigated for various values of the model parameters. The type of field statistics and photon bunching/antibunching effects has been examined.

Generation of femtosecond pulse of summary frequency is analyzed by both analytical and numerical methods under the simultaneous action of cubic and quadratic nonlinear responses of optical fiber. Using propagation invariants, this problem can be solved analytically in the framework of long-pulse approximation. Analytical solution was obtained and analyzed parametrically for the special choice of initial amplitudes of two basic waves, which allows full conversion of energy of interacting waves into the energy of the summary frequency wave (SFW) for the case of small self-action. Existence of various regimes of SFW generation as well as possibility for sufficient increase of conversion efficiency by the proper choice of initial amplitudes of two basic waves are shown and confirmed by computer simulation.

The problem of the application of different gauges for calculation of the fine shift of the S energy levels in the hydrogen-like atoms is considering up.

The quantum mechanical investigation of 4-ethyl-4-cyanobiphenyl molecule is represented in this work. The calculations of the structure and IR absorption spectra have been carried out using B3LYP method and 6-31G (d) basis set. The resulting structure was compared with the structure calculated by LEV-100 and calculated spectra were compared with experimental those.

The quantum mechanical investigation of 2-biphenylmethanol molecule is represented in this work. The calculations of the structure and IR absorption spectra have been carried out using B3LYP method and 6-31G (d) basis set. Two conformers of the molecule were found and then they were compared with the structure calculated by LEV-100.

On the basis of the matrix perturbation theory for eigenvalues and eigenvectors, a research into the intramolecular parameters of excited vibrational states has been performed. The formulas for determining the elements of tensors of vibrations form, kinematic and dynamic coefficients up to nth order of perturbation theory have been obtained.

The purpose of the work is to develop the method of registration of evolution the size of microparticles, which are formed in the alkali-halide crystals admixture aggregation. The used method is stimulated Brillouin scattering registration. The assembly for stimulated Brillouin scattering registration was collected and tested.

Spectral characteristics of multi-impurity crystals were investigated. Alkali-halide crystals with indium or nickel were used. Changes in the absorption, luminescence and excitation spectra of the crystals have been analyzed as a result of doping with additional impurities and as a result of the action of following factors: ionizing radiation, light, heating, storage of a crystal. Effects of additional impurities on the efficiency of formation of luminescence centers in the crystals are discussed.

We propose an approximate method for modeling the so-called Trojan wave packets of Rydberg states in a hydrogen-like atom subjected to a circularly polarized microwave field and a constant magnetic field. The method implies the reduction of the Schrodinger wave equation to a set of ordinary nonlinear differential equations for the parameters of the wave packet. Earlier we applied this method to solve the Schrodinger-like parabolic equation in nonlinear optics to describe misaligned beams in waveguide systems. The optimal values of the wave packet initial parameters are obtained. The numerical solution of the obtained differential equations show, that for these parameters the Trojan wave packet moves along a circle orbit.

We propose a new mechanism that can contribute to the spontaneous recombination of antihydrogen atoms in traps containing cold positron-antiproton plasma in the presence of a constant magnetic field. The latter plays a principal role restricting the motion of the positron in the transverse plane and, finally, prolonging the time during which the positron can lose its energy due to spontaneous radiation. Classical and quantum mechanical estimates are presented under the conditions close to those experimentally realized in the existing traps.

The object of this paper is self-access language learning and facilities self-access learners can use in their target language learning. The focus is on the beliefs of teachers and students, their changing roles in the class, and some self-access strategies and practical ideas to be helpful in the development and maintenance of self-access.

The paper presents analysis of the errors made by ESP (English for specific purposes) users which have been considered as typical. They occur as a result of misuse of resources of English grammar and tend to resist. Their origin and places of occurrence have also been discussed.

The importance of presentation and debate skills for scientists is obvious. However it may be difficult to find the right balance between the time spent on mastering these skills and that spent on science. Application of Pareto principle or “the eighty to twenty rule” can be a solution of this problem. In practice Students Speech and Debate Club can help young scientists master the required speech and debate skills with minimum of effort and maximum of result.

The procedure of measuring the birefringent plate parameters is discussed. It is shown that these parameters, both optical and geometric, can be measured with the help of Mach-Zehnder interferometer. The phase measured by means of an interferometer is a sum of several separate phases each of which is connected with a specific characteristic of the plate. Some of these phase are optical topological phases such as Rytov-Vladimirskii and Pancharantnam phases. Using their properties one can pick separate terms out of the general sum measured by the interferometer using the beams of different polarization.