Elena Shchepakina

Multi-Gaussian Schell-model beams

In a recent publication [Opt. Lett.37, 2970 (2012)10.1364/OL.37.002970], a novel class of planar stochastic sources, generating far fields with flat intensity profiles, was introduced. In this paper we examine the behavior of the spectral density and the state of coherence of beamlike fields generated by such sources on propagation in free space and linear isotropic random media. In particular, we find that at sufficiently large distances from the source, the medium destroys the flat intensity profile, even if it remains such for intermediate distances from the source.

Second-order statistics of stochastic electromagnetic beams propagating through non-Kolmogorov turbulence

We present a detailed investigation, qualitative and quantitative, on how the atmospheric turbulence with a non-Kolmogorov power spectrum affects the major statistics of stochastic electromagnetic beams, such as the spectral composition and the states of coherence and polarization. We suggest a detailed survey on how these properties evolve on propagation of beams generated by electromagnetic Gaussian Schell-model sources, depending on the fractal constant alpha of the atmospheric power spectrum.

Light scintillation in oceanic turbulence

The scintillation index of plane and spherical light waves as well as of a Gaussian beam, propagating in the clear-water weakly turbulent ocean, is revealed. The results are of utmost importance for underwater optical communications and sensing. An analysis of the threshold between the weak and strong regimes of oceanic turbulence is made, with the accent on the contribution from salinity-induced turbulence. It is found that strong oceanic turbulence can occur at distances as short as several meters, in striking contrast with atmospheric studies for which the typical distances are on the order of a kilometer.

Electromagnetic multi-Gaussian Schell-model beams

A recently introduced class of scalar multi-Gaussian Schell-model (MGSM) beams is extended to the electromagnetic domain. The realizability conditions and the beam conditions for the parameters of the new source are established. The behavior of the polarization properties of the beam on propagation in free space and in first-order imaging systems is investigated. The formation of the uniform polarization state in the central part of the transverse beam cross-section is explored in detail.

Color changes in stochastic light fields propagating in non-Kolmogorov turbulence

The dependence of spectral shifts and switches in optical stochastic beams propagating through nonclassic turbulent medium on the slope of the power spectrum of fluctuations in the refractive index is revealed.

Criterion for Thermal Explosion with Reactant Consumption in a Dusty Gas

The thermal explosion problem in a dusty gas is investigated. Dynamical regimes of the system are classified: slow regimes, thermal explosion with delay, thermal explosion (without delay). The critical transition conditions for the different dynamical regimes are analysed. We emphasize that the critical condition for transition between slow regimes and explosion with delay is a thermal explosion limit. The thermal explosion limit is described in the phase space by a so-called duck-trajectory. (The notion of duck-trajectory was introduced by Cartier for detailed investigation of relaxation oscillations.)

Random sources for optical frames

Analytical models for random sources producing far fields with frame-like intensity profiles are introduced. The frames can have polar and Cartesian symmetry and adjustable sharpness of the inner and outer edges. The frames are shape invariant throughout the far zone but expand due to diffraction with growing distance from the source. The generalization to multiple nested frames is also discussed. The applications of the frames are envisioned in material surface processing and particle trapping.

Rectangular Multi-Gaussian Schell-Model beams in atmospheric turbulence

Optical beams radiated by a recently introduced class of Rectangular Multi-Gaussian Schell-Model (RMGSM) source are examined on propagation in free space and in atmospheric turbulence, with both classic and non-classic power spectra of the refractive-index fluctuations. The expression for the cross-spectral density function of such beams has been derived and used for the analysis of their spectral density (average intensity). The RMGSM beams are shown to preserve the square/rectangular shape of the transverse intensity distribution and the maximum intensity level in the flat part for relatively large distances from the source on propagation in classic turbulence. This makes the novel beams attractive for free-space optical communications and surface processing in the presence of the atmosphere.

Black swans and canards in self-ignition problem

The paper is devoted to the investigation of thermal explosion (self-ignition) of reaction mixture situated in an inert porous medium. The analysis is based on qualitative theory of singularly perturbed systems, canards and black swans techniques.

Light scattering by three-dimensional objects with semi-hard boundaries.

We introduce analytical models for scattering potentials of particles that have ellipsoid-, cylinder-, and parallelepiped-like shapes and adjustable edge sharpness with the help of the three-dimensional versions of the multi-Gaussian functions. The far fields produced upon scattering from such potentials are examined in detail and are shown to qualitatively and quantitatively depend on the scatterers symmetry type as well as its orientation and edge sharpness.