S. A. Fedorov

Exciton-like electromagnetic excitations in non-ideal microcavity supercrystals.

We study localized photonic excitations in a quasi-two-dimensional non-ideal binary microcavity lattice with use of the virtual crystal approximation. The effect of point defects (vacancies) on the excitation spectrum is investigated by numerical modelling. We obtain the dispersion and the energy gap of the electromagnetic excitations which may be considered as Frenkel exciton-like quasiparticles and analyze the dependence of their density of states on the defect concentrations in a microcavity supercrystal.

Transformation of the Polariton Spectrum of Nonideal Topologically Ordered Superlattices

The transformation of the polariton spectrum of a nonideal superlattice (a one-dimensional crystal with two elements, layers, in a unit cell) caused by the presence of randomly embedded foreign (with respect to an ideal superlattice) impurity layers is investigated in the framework of the virtual crystal approximation. The obtained specific features of the energy gap as a function of concentration for different values of the polariton branch number testify that the energy structure of the superlattice can be changed significantly by embedding certain impurities into it.

Propagation of light in a quasi-two-dimensional Si/SiO2 superlattice with variable strip thickness

The propagation of an electromagnetic excitation localized in a nonideal quasi-two-dimensional Si/SiO2 system that constitutes a topologically ordered set of strips with a random number of defect strips is numerically simulated within the virtual crystal approximation. The defect strips differ from the basic strips (for an ideal periodic structure) in both the composition and the thickness. The concentration dependence of the lowest photonic bandgap of the nonideal striped Si/SiO2 film is studied. It is found that the presence of foreign layers in this nonideal superlattice causes a considerable renormalization of its polariton spectrum.

One-magnon light scattering in exchange-noncollinear Nd2CuO4

Abstract It is shown that in an exchange-noncollinear four-sublattice antiferromagnet Nd 2 CuO 4 an anomalously high intensity of light scattering from the exchange magnon should be observed. It makes it possible to determine directly the constant of the biquadratic exchange interaction.

Light scattering on magnons in many-sublattice antiferromagnets in a magnetic field

A study is made of Raman light scattering on magnons in a many-sublattice antiferromagnet in a magnetic field parallel to the easy axis. An investigation method is developed which makes possible the optimum use of the magnetic symmetry. As an example, the scattering in a four-sublattice rhombic antiferromagnet at T=0 for all realised magnetically ordered phases is investigated. The form of the scattering tensor is obtained and the dependence of its components on the magnetic field is calculated. Emphasis is given to the study of light scattering on exchange modes. The contribution of the exchange mechanism to the single-magnon scattering tensor is discussed.

Polaritons in a nonideal array of ultracold quantum dots

We develop a numerical model for a defect-containing square lattice of microcavities with embedded ultracold atomic clusters (quantum dots). It is assumed that certain fractions of quantum dots and cavities are absent, which leads to transformation of polariton spectrum of the overall structure. The dispersion relations for polaritonic modes are derived as functions of defect concentrations and on this basis the band gap, the effective masses of lower and upper dispersion branch polaritons as well as their densities of states are evaluated.

Gyrotropy of molecular crystals with vacancies

A microscopic analysis is made of the gyrotropy of molecular crystals with vacancies. For impurity-free systems with a primitive lattice, the concentration dependence of rotatability in two frequency regions is studied.

Optical activity of dielectric superlattices with defects

Natural optical activity of a nonideal 1D multilayer system is considered phenomenologically and the concentration dependence of its specific rotation angle is simulated numerically. As a model system, the two-sublattice SiO2 LC structure was chosen. Specific gyrotropy features caused by the corresponding disordering types of the studied systems were revealed. Based on the developed phenomenological theory, the frequency dependence of the specific rotation angle of the polarization plane of linearly polarized light was studied for the case of a molecular-crystal multilayer system whose layers contain pointlike defects. This creates additional possibilities for simulating optically active multilayer composite materials.

One-magnon light scattering in exchange-noncollinear magnets

Abstract The one-magnon light scattering in different types of magnets whose magnetic structure is noncollinear in exchange approximation has been studied theoretically with the help of symmetry analysis. The role of the exchange mechanism of scattering by acoustic and exchange modes has been elucidated. It is shown that the intensity of Raman light scattering by exchange magnons exceed far the intensity related to acoustic ones in opposite to the situation found in collinear magnetic structures.

Polariton excitations in a non-ideal array of microcavities with quantum dots

The polariton spectrum of a one-dimensional non-ideal array of coupled microcavities containing quantum dots has been studied. The specific features of the dispersion of electromagnetic excitations, which are induced in this system both by a variation in the distance between the adjacent microcavities and by a variation in the composition of the quantum dots, have been investigated using the numerical simulation within the framework of the virtual crystal approximation. The density of states of the quasiparticles under consideration has been determined.