G. B. Sochilin

On scattering of electromagnetic radiation by inhomogeneities of the velocity of motion of the medium

Analysis of the scattering of a plane monochromatic electromagnetic wave by an inhomogeneity of the velocity of motion of the medium is carried out. The inhomogeneity corresponds to the rotation of a finite portion of the medium with a constant angular velocity under the conditions of spatial homogeneity of the permittivity and the permeability. The case of oblique incidence of the wave is studied. The scattering cross sections for an inhomogeneity having the shape of a cylinder or a sphere of different dimensions are found for different angles of incidence of radiation.

States of a quantum particle exhibiting complex quasi-energy in a dynamic trap

States of a single quantum particle in a one-dimensional dynamic trap, which correspond to complex values of quasi-energy, are found. The trap is described by a square potential well with periodic smallamplitude oscillations of barrier position. The specific feature of the problem is the fact that the dynamic trap affords simultaneous localization and excitation of the confined particle. The complex nature of the quasienergy is caused by finite probability of particle escape from the trap due to finite depth of the potential well. Within the framework of the second-order perturbation theory with respect to modulation depth, the dependence of the decay rate of the states on modulation frequency is determined, which proves to be nonmonotonic.

On focusing of terahertz radiation beams and pulses

We show that, for terahertz (THz) radiation, the effective focal length of a lens differs significantly from its geometrical-optics (nominal) focal length. As a pulse of THz radiation with a bell-shaped (Gaussian) transverse profile is incident on a lens, the field-amplitude distribution in the nominally focal plane of the lens may radically change, up to the formation of dips in the paraxial region. These changes in the spatiotemporal shape of the beam (pulse) may considerably distort the results of pulsed THz spectroscopy. These distortions can be minimized by using media with anomalous dispersion, including metamaterials.

On reflection of terahertz radiation from a rough surface

We computationally analyze the influence of random inhomogeneities of the interface surface between two media that are diagnosed by the pulsed THz spectroscopy method. The statistics of inhomogeneities is characterized by the rms dispersion and correlation radius. The medium to be diagnosed is modeled by a Lorentz contour, the position and the width of which can serve as recognizable indicators. For monochromatic radiation and for a radiation pulse with a wide spectrum (close to the video pulse), a signal at a “point” detector is calculated in the absence and in the presence of inhomogeneities. The results yield conditions under which inhomogeneities significantly affect the recognition of different substances.

Manifestations of Radiation Scattering in the Method of Pulsed Terahertz Spectroscopy

The scattering of broadband terahertz pulses on a rough surface of a semi-infinite medium has been analyzed by a modified Monte Carlo method, which takes into account the radiation phase. The results have been compared with a simplified analytic expression that allows generalization in the case of layered media and the presence of volumetric scattering. These results allow a simple way to exclude or reduce the scattering influence on the recovery of the media characteristics in the method of pulse terahertz spectroscopy to be suggested.

On diffraction of radiation packets with ultimately short duration

The inference of the work by V.A. Banakh that there is an absence of diffraction of optical radiation in the limit of zero pulse duration is analyzed.

On reflection of radiation from moving objects

An analytical expression for the field reflected from a nonuniformity of the velocity of a moving medium is obtained. Specific features of the reflected radiation depending on the velocity and sizes of the non-uniformity domain and on the angle of incidence of radiation relative to the direction of motion are studied. The feasibility of experimental detection of the reflected radiation is demonstrated.