[en] The spatial intensity distribution of radiation propagating in semi-infinite directional coupler arrays with different dependences of coupling constants on the fibre number is studied. (fibre and integrated optical elements and devices)

[en] It is shown that upon two-photon excitation of bi-excitons from the ground state by a powerful optical pulse, a weak laser pulse is amplified within the M band. (nonlinear optical phenomena and devices)

[en] Nonstationary transmission (reflection) of two time-separated ultrashort laser pulses by thin semiconductor films is studied. Photons of one of these pulses generate biexcitons in the films due to two-photon absorption from the crystal ground state, while photons of the other pulse induce an optical exciton - biexciton conversion. Several basically new effects in nonstationary light transmission (reflection) are found and interpreted. (nonlinear optical phenomena)

[en] The relationships governing nonlinear transient transmission and reflection of ultrashort resonant laser radiation pulses with rectangular and Gaussian profiles by a thin semiconductor film were investigated taking into account the exciton-photon interaction and the concentration enhancement of the dipole moment of the exciton transition. It is shown that the transmission of a Gaussian pulse is characterised by the formation of two subpulses with identical areas, which are separated in time and have different profiles. (nonlinear optical phenomena)

[en] A set of nonlinear evolution equations describing the dynamics of atoms, molecules, and photons in the course of stimulated atomic-molecular conversion in a Bose-Einstein condensate is derived and studied in the mean-field approximation. It is shown that conversion can be periodic or aperiodic in time, the rate of the process being determined to a considerable extent by the initial density of particles and by the initial phase difference. Depending on the initial conditions, various conversion modes can be realized. The possibility of stabilization of a special state (of rest) of the system for nonzero initial number densities of particles is predicted. It is pointed out that coherence of a Bose condensate of atoms, molecules, and photons predetermines the possibility of phase control of the conversion process

[en] The characteristic features of the self-reflection of a powerful electromagnetic wave in a system of coherent excitons and biexcitons in semiconductors were investigated as one of the manifestations of the nonlinear optical skin effect. It was found that a monotonically decreasing standing wave with an exponentially falling spatial tail is formed in the surface region of a semiconductor. Under the influence of the field of a powerful pulse, an optically homogeneous medium is converted into one with distributed feedback. The appearance of spatially separated narrow peaks of the refractive index, extinction coefficient, and reflection coefficient is predicted. (nonlinear optical phenomena)

[en] An exact analytic solution is obtained for the problem of light propagation in a three-core nonlinear directional coupler with identical parallel fibres in the geometry of a regular triangle for an arbitrary dependence of the propagation constant on the light intensity. (nonlinear optical phenomena)

[en] Specific features of the transmission of ultrashort resonance laser pulses by a thin semiconductor film are studied taking into account the two-photon exciton-biexciton conversion. It is shown that ultrashort pulses are transformed into shorter solitary pulses or a train of pulses whose duration is determined to a large extent by parameters of a nonlinear medium. (nonlinear optical phenomena)

[en] Peculiarities of reflection at the end face of a semi-infinite semiconductor in a two-pulse regime are studied. The reflection functions behave in a complex and ambiguous manner governed by the amplitudes of the fields of incident pulses. The possibility of a complete bleaching of the medium for the field in the M-band is predicted. (nonlinear optical phenomena)

[en] The features of light reflection from the interface of a semi-infinite semiconductor are studied upon two-pulse, two-photon excitation of biexcitons from the crystal ground state. It is shown that the reflectivity is a complex multistable function of the amplitudes of the fields of incident pulses. The appearence of solitary closed domains or horn-shaped structures is predicted. (nonlinear optical phenomena)