The kinetics of a strongly nonequilibrium state of electrons and holes excited in quantum dots by a long laser pulse in the p-states are studied using the timeresolved photoluminescence. Three bands of the transient photoluminescence spectra were identified, and the ignition and decay of each of them was investigated. The complex picture of the time evolution of the bands is explained by the fast processes of cascade intraband relaxation and the Pauli exclusion principle. The durations of formation and decay for each of the photoluminescence bands are determined.

We demonstrate that in the study of time-resolved photoluminescence the signatures of biexcitons in QDs can manifest themselves even when the system is excited by long laser pulses with their duration of the order of several tens of picoseconds. To describe the results of our measurements we propose an elegant theoretical model. It is based on the introduction of auxiliary sources in the rate equations. The parameters of the sources are determined by fitting the analytical solution of these equations that describes the full emission of the system to the experimental results obtained. Having found the parameters of the auxiliary sources we can determine the temporal dependences of the radiation from excitons and biexcitons separately. We find the spectral positions of the exciton and biexciton emission bands, their widths, and the biexciton binding energy.

The dependences of the fundamental transition on the semiconductor quantum dot size obtained experimentally at various temperatures using different measuring methods are analyzed and compared. The possibility to extrapolate the results for the case of arbitrary temperature is discussed.

The dependences of the fundamental transition on the quantum dot size obtained experimentally at various temperatures using different measuring methods are analyzed and compared. The possibility to extrapolate the results for the case of arbitrary temperature is discussed.

A new lasing mechanism for semiconductors like CuCl, CuBr is proposed based on the two-photon pumping of biexcitons from the ground state of the crystal and generation or amplification of light in the region of M-band of luminescence due to the optical exciton-biexciton conversion. It was shown that the net gain essentially depends on the level of two-photon pumping and rapidly decreases deep into the crystal due to the spatial depletion of pump radiation. Estimations for CuCl give the values of lasing photons with the energy about 3,2 eV and the maximum small signal gain about the value of the exciton absorption coefficient.

We propose and theoretically investigate a two-photon four wave mixing experiment to probe for BEC of excitons in Cu2O thin films. A relatively simple set of equations describing the dynamics of the system is obtained for a particular configuration of the exciting beams, and numerical and approximate analytical solutions are found. The resulting phase-conjugated signal vs. the delay time between the pump and probe pulses yields a direct measure of the time evolution of the exciton condensate, and exhibit peaks when the film thickness is a multiple of a half wavelength of light.

A theoretical and numerical analysis of the transmission of phase-modulated laser pulses through a thin film with excitonic nonlinearity is performed. It is shown that, by choosing the modulation law, one can efficiently control the optical nonlinearity of the film down to the inversion of the sign of nonlinearity.

Taking into account the exciton-photon and elastic exciton-exciton interactions we investigated peculiarities of transmission of supershort light pulses by thin semiconductor films. We predict the appearance of time dependent phase modulation and dynamical red and blue shifts of transmitted pulse.

The time evolution of an intense polariton wave has been studied in the framework of a microscopic approach. It has been shown that due to polariton–polariton scattering a significant polariton wave depletion takes place in a comparatively short time interval. The condensate decay occurs in the form of multiple echo signals. Distribution-function dynamics of scattered polaritons have been investigated.

Time evolution of a nonequilibrium polariton condensate has been studied in the framework of at microscopic approach. It has been shown that due to polariton-polariton scattering a significant condensate depletion takes place in a comparatively short time interval. The condensate decay occurs in the form of multiple echo signals. Distribution-function dynamics of noncondensate polaritons have been investigated

The time evolution of non-equilibrium polariton condensate has been studied in the framework of microscopic approach. It has been shown that due to polariton-polariton scattering a significant condensate depletion takes place in a comparatively short time interval. The condensate decay occurs in the form of multiple echo signals. Distribution function dynamics of non-condensate polaritons has been investigated. It has been shown that there are stochastic ripples on the smooth curve of the distribution function.

A derivation of the equations describing kinetic and dynamic properties of a high-density polariton system excited in direct-gap semiconductors by an external laser field is given. The Keldysh diagram technique for non-equilibrium processes formulated in terms of functional equations is used. With functional Legendre transformation, Dyson equations are derived for normal and abnormal connected Keldysh-Green's functions, which describe quantum fluctuations in the system, and also for a coherent part of the polariton field. The vertices in the Dyson equation are calculated using perturbation theory. Boltzmann-type kinetic equations for the case of small time inhomogeneity of the system are obtained in Born approximation.

AbstractA derivation of the equations is given describing kinetic and dynamic properties of a high density polariton system excited in direct‐gap semiconductors by an external laser field. Keldysh diagram technique for non‐equilibrium processes formulated in terms of functionals is used. Using functional Legendre transformation the Dyson equations are obtained for normal and abnormal connected Keldysh‐Green's functions, which describe quantum fluctuations in the system, as well as for a coherent amplitude of the polariton field. The vertices in the Dyson equations are calculated using perturbation theory.

The absorption coefficient of weak electromagnetic radiation of semiconductors in a strong field of an arbitrarily polarized electromagnetic wave which induces resonance one-photon transitions of an electron between the edge of the valence band and the edge of the conduction band has been evaluated. The dependence of light absorption and amplification upon the type of its polarization has been investigated. It has been shown that at finite temperatures the absorption coefficient can have additional features which have not been discussed earlier in literature.

The spontaneous recombination radiation spectrum of a semiconductor in the external field of an arbitrary polarized laser wave in the saturation state is investigated. Considerable dependence of the electromagnetic energy radiation rate of predetermined frequency upon the polarization type of the exciting field is predicted.

Two experiments on Compton scattering in an intensive laser radiation field, carried out in two different inertial reference systems are considered. It is shown that the results of both experiments transformed in a certain fixed reference system differ from each other, as a consequence of the relativity of time and of the way of describing the laser field accepted in this paper.