The anisotropy and time-delayed nature of external feedback modify polarization switching thresholds and dynamical phenomena which are studied analytically and numerically for sensitivity to misalignment of the axes of intrinsic and external anisotropies.

Some types of regular and chaotic passive Q switching regimes round several steady points in CO₂ laser with methanol as saturable absorber are obtained experimentally and theoretical model to explain their appearance is proposed. Phase portraits and the first peak intensity return maps are used to analyze them. Complicated regular regimes with some types of dynamics between two or three steady states for two longitudinal modes are considered both with and without intensive giant pulse between oscillations of each of modes. Some kinds of chaos round several points are proposed and reasons for their appearance are discussed.

Long and short wavelength spatio-temporal instabilities have been theoretically found in transverse section of an anisotropic dye laser and expression for the pattern sizes, frequencies and amplitudes have been derived as function of the rate of Brownian Rotation.

Nonlinear dynamics due to the phase modulation instability and resulting in the bistability for the regime of formation of ultrashort pulses is investigated. We studied the regime of breathing ultrashort pulse due to this instability. Other possible established regime connects with an increase in the number of stable stationary ultrashort pulses in laser cavity. It is shown that type of established regime depends on initial conditions.

The studies on transients in waveguide 1D and 2D laser arrays with the diffraction coupling in Talbot cavities are presented. The transient behavior essentially depends on the selectivity of an external cavity which are determinated by the number of lasers, dimensionality and filling configuration of arrays involved. Probabilities of the in- phase generation as a result of transient are calculated. The possibility of the in-phase generation forming during the transient is discussed.

The problem of initiating of laser-induced damage of ideal microspherical and microdisk resonators and nature of processes limiting ultimate pump intensity of the resonators are considered in this paper. Electrodynamic processes are supposed to play major role in initiating of laser-induced damage of the resonators and theoretical model to describe local increasing of high-power electromagnetic field in passive microresonator is presented to study the processes. It is based on idea of formation of unstable field structure in resonant dielectric microcavity connected with formation of positive feedbacks resulting in light-induced variation of quality factor and its spectrum. Possibility for field instability to arise is estimated making use of model of diffraction of high-power plane wave on sphere and microdisk resulting in formation of resonant whispering-gallery mode. Field instability is shown to be threshold-like phenomenon. There are estimated ultimate amplitude of incident pump wave and field amplification in the microsphere and microdisk.

Backward light scattering processes always take place in fiber lasers. They create additional feedback in laser resonator changing qualitatively the laser operation. We have described for the first time the mechanisms of their influence on lasing in number of fiber configurations. The understanding of the mechanisms allows us to get several important scientific results suitable for rapid practical applications in the process of elaboration of new fiber sources of light.

A theoretical investigation was made of the dynamics of generation of an optical field in a Fabry-Perot cavity with an active medium and a bleachible filter, considered in the limiting case of an infinitely large aperture and in the case of real laser. Self-similar wave solutions were obtained in the first case, wave velocity and frequency were determined. For the second case it is created the spatiotemporal numerical model which permits to find the states of the optical field E(x,z,t) at the every cavity round-trip time. Using this model we investigated the formation of the transverse structure of laser fields at the different parameters of active media and saturable absorber. It is found the stationary quasi-periodic waves traveling across the finite aperture at a slow response time of an active medium. Their structure and the conditions of their excitation are considered.

Nonlinear interactions of counter propagating waves take place in various nonlinear optical processes attracting attentions of investigators for many years. This is due to problems having a practical importance (for example, wave front conjugation). However, a number of factors that influence on processes quality were exposed by investigators. There is an instability appearance in the system of counter propagating waves among them. An analytical solution for the scheme of two wave have been obtained by now only for strict counter interaction. In the present report some instabilities development is demonstrated by the examples obtained from the mathematical simulation experiments. As an explanation of the some reasons of instability, the question of convective instability (along the interaction region) in the system of counter propagating noncollinear plane waves with unequal amplitudes is studied.

We present results of direct computer simulations of formation of laser bullets--3D localized (soliton-like) structures of coherent radiation in media with saturable optical absorption and amplification and frequency dispersion. Stable stationary symmetric and pulsing asymmetric laser bullets are demonstrated. Superstability of these dissipative solitons and absence of drift of their main parameters give good reason to believe that these structures are promising for applications in the field of optical information processing.

A general model for nonlinear optical frequency conversion devices based on second-order parametric processes is presented. The main emphasis is on optical parametric oscillators. First, the model allows propagation in any direction in uniaxial or biaxial crystals, and diffraction and walk-off are included. Alternative numerical methods for solving the equations for the nonlinear interaction in the birefringent crystal are compared. Second, techniques for modeling temporal walk-off are considered. This is important in devices operating with short pulses or wide spectra. Third, initiation of parametric oscillation from spontaneous emission noise is modeled by adding random noise to the signals. The random nature of the noise initiation process leads to pulse to pulse fluctuations in energy, spectrum, and transverse beam shape. The fluctuations in transverse shape are small for narrow pump beams, but for wide pump beams they can be significant. Finally, thermal effects are considered. In devices with high average power, even a small absorption of one of the interacting beams can cause a temperature gradient in the nonlinear crystal. This temperature gradient leads to thermal lensing and spatially varying phase matching.

Parametric generation of light at pumping by Bessel light beam has been investigated. Advantages of such pumping over the use of Gaussian light beams have been revealed. A theory of azimuth-matched nonlinear interaction of Bessel light beams has been developed. It is shown that at such an interaction in the parametric generator the maximum coupling coefficient is realized and no destruction of the spatial structure of introcavity fields at high coefficients of conversion occurs. This opens up the possibility of increasing the energy conversion coefficient of the input Bessel beam compared to the Gaussian beam.

It has been designed and applied the method of transfer matrix for layered structures with second order nonlinearity, as new technique to simulate spectral characteristics of semiconductor microcavities. The nonlinearity of single layer is simulated by transfer matrix with 4 X 4 dimensions. Light intensity distributions and spectral dependencies for generator of second harmonic have been calculated. It has been shown that the most effective direction of second harmonic wave is not coincide with direction of incident wave. It is demonstrated the university of suggested algorithm and capability to extend it for other types of cavities and nonlinearities.

Here we study the open modification of the Jaynes-Cummings model that is the coupled system of the dressed atom and the quantized mode. The mode is initially in the coherent quantum state exhibiting the Poissonian photon statistics. When the quasienergy levels of the dressed atom cross the mean number of photons (n) in the mode undergoes high- amplitude oscillations. Numeric results show that each time the value of (n) falls the photon statistics becomes more regular. Instantaneously, the statistics can become sub- Poissonian with the Fano factor F equalsV (Delta) n²/(n) being many times as small as unity. The above observation provides the evidence that the photons undergo correlated absorption, i.e., they tend to disappear in twos, in threes, etc.

Light amplification without population inversion and absorption with inversion driven by quantum coherent interferences in a closed three level V-type system is studied from the point of view of two color dressed state basis. Approximate analytic time dependent solutions, for coherences and population distribution are derived, and compared with full numerical solutions. Steady state quantities are also calculated, and the conditions under which the system exhibits gain with and without inversion, in the dressed state representation are derived. It is found that for a weak probe laser field light amplification without inversion may occur, for a range of system parameters, in both the bare and the dressed state representations.

A process of non-classical (squeezed) light generation by electron beam in a field of a strong external electromagnetic wave is considered. Each electron move in such field along the figure of eight therefore in the direction of the wave vector there is an oscillations of electrons position with a double frequency of the wave. For input noises a degenerate parametric regime is realized therefore a state of an output field can be squeezed. A squeezing coefficient is estimated and for a large amplitude of the input field it can be considerable.

The published experimental works are analyzed in details in which announcements were made of the observation of some effects which might be associated with the phenomenon of induced (gamma) -emission. It is shown that practically in all cases the obtaining of experimental data was accompanied by circumstances which made difficult to interpret them as the indications of the induced (gamma) -emission effect. The exclusion is one of the experiments by S.I. Bondarevskii's group in which they observed a decay acceleration of the ^123mTe (gamma) -source cooled down to the liquid helium temperature as compared with decay of other similar (gamma) - source situated at room temperature. However the small magnitude of the observed effect and absence of control measurements require careful repetition of this experiment.

Some results in substantiating for a feasible (gamma) -lasing experiment are considered. Self microplasma (SM) existence in active medium (AM) is set up. SM-density at other pumping types is more by several orders than one at soft prompt transplantation of excited nuclei (SPTEN). Hence schemes of amplification without inversion (AWI) are broken down by the SM. Types of AWI and (gamma) -lasers steady against SM are revealed. Distance L'-effect on Moessbauer spectrum and on a (gamma) -lasing is predicted. Radiation-heat regimes and (gamma) -lasing conditions (induced, super-radiant) are studied. Difficulties of gas-AM (in beams) are analyzed. New candidate ⁵⁸Co (28.1 KeV, 1.51 10^-5 s) is suggested. SPTEN efficiency is drastically increased on base of new device, so called `atomic (molecular) multi-beam emitter' proposed also for industrial laser isotope separation.

An induced gamma emission (IGE) upon the transition Sn(119 m₂) + hv_res(65.66 keV) yields Sn(119m₁) + 2hv_res was triggered in the polycrystal matrix ^119m(2)SnO₂ by its cooling to a temperature of 78 K. A measured relative value of the IGE output ((epsilon) (SnO₂) equals 0.00014 and (epsilon) (SnO) M(78 K) equals 0.235 for ^119m(2)SnO₂ and f_M(10 K) equals 0.021 for ^119m(2)SnO.

I have investigated analytical simulation of the possibility of application super-strong, ultrafast laser radiation for nucleosynthesis of ²⁶Al, ²⁶Al^m (Al-Mg-cycle) in cosmic regolith using products of the reaction ³He(d,p)⁴He, and other light accelerated charged particles. It may be laser propulsion with annihilation of cosmic propillents a matter.

Calculations of induced gamma emission potential output spectra from the 178Hfm2 isomer are developed assuming three decay modes through the fast Yrast channel, the 78 ns channel and the 4 s channel. Temporal and energy distributions of energy are examined. These spectra are then compared to potential regions of interest for various uses with an emphasis on medical applications.