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Khadzhi, P. I.

Publications and source records attributed to Khadzhi, P. I..

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Polariton-Type Dispersion Laws for Three-Level Atoms Interacting with Two Laser Radiation Pulses

Behavioral features of polariton dispersion laws are studied for three-level atoms interacting with two coherent laser radiation pulses with frequencies ω{sub 1} and ω{sub 2} that are in resonance with optically resolved one-photon transitions between levels 1⇆2 and 2⇆3, respectively, and with regard to the direct two-photon transition between levels 1 and 3. The approximation of given photon densities of both pulses compared with the densities of atoms is used. It is shown that the dispersion law consists of three branches whose position and shape are determined by the Rabi frequencies of the above three optical transitions and the photon densities in both pulses. The direct consideration of all three optical transitions leads to the dependence of the dispersion law of atomic polaritons on a new quantum parameter—the phase difference between the three Rabi frequencies. The values of the system parameters are found for which the branches of the dispersion law may intersect. The concept of the surface of the dispersion law is introduced in the dependence of the eigenfrequencies of atomic polaritons on the photon wave vectors in both pulses.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Peculiarities in Transmission (Reflection) of Ultrashort Resonant Laser Pulses by a Thin Semiconductor Film in the Conditions of Exciton and Biexciton Excitation

We have studied the nonstationary transmission of two ultrashort laser pulses incident on a thin film. The radiation frequency of one of these pulses is in resonance with the two-photon transition from the ground state of the crystal to the biexciton state, while the other pulse coherently mixes the exciton and biexciton states, leading to strong renormalization of the energy spectrum of the crystal. We have obtained a system of nonlinear equations describing the time evolution of the exciton and biexciton amplitudes and the fields of three pulses transmitted through the film. We have analyzed the effect of amplitudes and widths of incident pulsed and of the time delay between them on the peculiarities of film transmission of these pulses. We have predicted the effect of a substantial time delay in the generation of the pulse transmitted through the film relative to the incident pulse, which is in resonance with the exciton–biexciton transition frequency. The possibility of generation of a precursor, viz., a pulse transmitted through the film sooner than the peak of the incident pulse reaches the film, as well as possibility of generation of a reflected pulse in the absence of the incident pulse, has been proven.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Metastable Bound States of the Two-Dimensional Bimagnetoexcitons in the Lowest Landau Levels Approximation

The possible existence of the bound states of the interacting two-dimensional (2D) magnetoexcitons in the lowest Landau levels (LLLs) approximation was investigated using the Landau gauge description. The magnetoexcitons taking part in the formation of the bound state with resultant wave vector k=0 have opposite in-plane wave vectors k and −k and look as two electric dipoles with the arms oriented in-plane perpendicularly to the corresponding wave vectors. The bound state of two antiparallel dipoles moving with equal probability in any direction of the plane with equal but antiparallel wave vectors is characterized by the variational wave function of the relative motion φ{sub n}(k) depending on the modulus |k|. The spins of two electrons and the effective spins of two holes forming the bound states were combined separately in the symmetric or in the antisymmetric forms (↑↓ +η ↓↑) with the same parameter η=±1 for electrons and holes. In the case of the variational wave function φ{sub 2}(k)=(8α{sup 3}){sup 1/2}k{sup 2}l{sub 0}{sup 2}exp [−αk{sup 2}l{sub 0}{sup 2}] the maximum density of the magnetoexcitons in the momentum space representation is concentrated on the in-plane ring with the radius k{sub r}=1/(√αl{sub 0}). The stable bound states of the bimagnetoexciton molecule do not exist for both spin orientations. Instead of them, a deep metastable bound state with the activation barrier comparable with the ionization potential I{sub l} of the magnetoexciton with k=0 was revealed in the case η=1 and α=0.5. In the case η=−1 and α=3.4 only a shallow metastable bound state can appear.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Nonlinear Dynamics of Parametric Oscillations of Polaritons in a Microcavity

The dynamics of polaritons in a microcavity in the parametric oscillator mode, when two pump polaritons turn into the signal and idler polaritons and vice versa, has been studied. The pumping is carried out using two lasers with close frequencies. Analytical solutions of the system of nonlinear differential equations have been obtained. The periodic and aperiodic modes of the transformation of a pair of pump polaritons into signal and idler polaritons have been found.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Dynamics of a Dipolariton Optical Parametric Oscillator in a Semiconductor Microcavity

The dynamics of dipolariton states in a planar microcavity has been studied upon pumping of a state corresponding to the middle dipolariton branch. It has been shown that, under exact resonance conditions, both periodic and aperiodic regimes of conversion of pump dipolaritons to dipolaritons of idler and signal modes occur. The periodic regime of conversion of signal and idler dipolaritons without involving pump dipolaritons on the middle branch has also been analyzed.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Anharmonic Bloch oscillations in a waveguide array

Using the coupled-wave method, we consider anharmonic Bloch oscillations of light in an array of waveguides, taking into account the coupling between waveguides up to the third order. It is shown that the beam trajectory is periodic, with the trajectory oscillating within a single period. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗