Igor A. Grishin

Scattering matrices for large ice crystal particles

The problem of light scattering by ice crystal particles whose sizes are essentially larger than the incident wavelength is divided into two parts. First, the scattered field is represented as a set of plane-parallel outgoing beams in the near zone of the particle. Then, in the far zone the scattered field is represented as a result of both diffraction and interference of these beams within the framework of physical optics. A proper ray-tracing algorithm for calculation of the amplitude (Jones) scattering matrix is developed and applied. For large particles, a number of reduced Mueller matrices are introduced and discussed, since the pure Mueller matrix obtained from the Jones matrix becomes a rather cumbersome and quickly oscillating value. Backscattering by hexagonal ice crystals, including polarization properties, is considered in detail.

Raman band intensities of tellurite glasses

Raman spectra of TeO2-based glasses doped with WO3, ZnO, GeO2, TiO2, MoO3, and Sb2O3 are measured. The intensity of bands in the Raman spectra of MoO3-TeO2 and MoO3-WO3-TeO2 glasses is shown to be 80-95 times higher than that for silica glass. It is shown that these glasses can be considered as one of the most promising materials for Raman fiber amplifiers.

Light backscattering by hexagonal ice crystals

Abstract Backscattering of light by hexagonal ice columns and plates has been calculated by means of a ray-tracing code. It is shown that backscattering by the hexagonal ice cylinders at their arbitrary orientations is caused by a peculiar corner-reflector effect. A gigantic peak of backscattering is found at the angle of about 32.5° between the principal axis of a particle and the incidence direction for both hexagonal ice columns and plates. This peak is explained by multiple total internal reflections inside the crystals that take place for a part of incident rays. The obtained results on backscattering efficiency allow one to calculate backscattering by an ensemble of the hexagonal ice cylinders of various sizes, shapes and orientations. Slant lidar remote sensing of cirrus clouds for discrimination between aligned columns and plates is suggested as an application of the results obtained.

Backscattering peak of hexagonal ice columns and plates.

The backward cross section of hexagonal ice crystals of arbitrary orientation is calculated for visible light by means of a ray-tracing code. It is shown that backscattering of the tilted crystals is caused by a corner-reflector-like effect. A very large peak of backscattering is found for a tilt of 32.5 degrees between the principal particle axis and the incidence direction. This peak is caused by multiple total internal reflections for part of the rays that are incident upon the skewed rectangular faces. Slant lidar measurements for remote sensing of cirrus clouds are proposed.

Shape characterization of a large nonspherical particle by use of its Fraunhofer diffraction pattern

We characterize the shape of a large nonspherical particle by means of the two-dimensional Fourier transformation of its diffraction pattern, called the S function. The main properties of S functions are considered. Some ways in which to retrieve the geometric parameters of a particle by use of its S function are discussed. In particular, the parameter of nonsphericity of a particle is defined by means of the S function.

Spectroscopic properties of new BaCl2–BaO–TeO2 tellurite glasses for fibre and integrated optics applications

We present results of the study of transmittance and Raman spectra in BaCl2‐BaO‐TeO2 glasses possessing intense spontaneous Raman scattering which are promising for the development of integrated and fibre stimulated Raman lasers. Compared with oxide‐tellurite systems these glasses are found to be transparent in a wider wavelength range, from 350nm to 6.5 µm. A band near 765cm −1 is found to arise in the Raman spectra of the glasses with total BaO and BaCl2 content exceeding 30mol%. The band turns out to be 70‐80 times as intense as the main Raman band with maximum near 440cm −1 in SiO2 glass. Quantum-chemical calculations of the structure and vibrational spectra of the glasses show that the 765cm −1 band is caused mainly by vibrations of O3Te‐O − and O2Te=O non-bridging oxygen atoms. (Some figures in this article are in colour only in the electronic version)

Monte Carlo simulation of radiation transfer in optically anisotropic clouds

A mathematical model and a Monte Carlo algorithm were developed to simulate radiation transfer in dispersive media that is optically anisotropic with respect to zenith angle of the light beam. The algorithm was created with the purpose to simulate radiation transfer processes in the atmosphere with optically anisotropic clouds (for instance, cirrus clouds). A numerical experiment was performed for a cloud with ice crystals of hexagonal cylinder shape. We compared results for scattering media with particles stochastically oriented in a horizontal plane and in space. It was shown that orientation of particles could strongly affect the albedo of clouds and the shape of halos.

Polarized light backscatter by hexagonal ice crystal particles

Lidar backscatter by hexagonal ice cylinders of cirrus clouds is considered within the framework of both geometric optics and physical optics approaches. Within geometric optics, reasons of great backscattering peak and of large magnitudes of the depolarization ratio are investigated and explained. An approach including diffraction and interference phenomena is discussed.

Scattering (Mueller) matrices for ice crystal particles of cirrus clouds

Scattering (Mueller) matrices are calculated for typical convex ice crystal shapes: hexagonal prism, tapered hexagonal prism, bullet, and pyramid, the particles being randomly oriented in space. A pure geometric optics approach is used for the calculations. Besides. a physical optics approach to the problem is considered. Possible physical optics corrections to the geometric optics Mueller matrix are discussed.

Mueller matrix for randomly oriented ice crystal particles

Scattering matrices are calculated for randomly oriented ice crystal particles of various shapes: hexagonal prism, tapered hexagonal prism, bullet, and pyramid, a pure geometric optics approach is used. Within the approach, scattering peaks at forward and backward directions are separated. As a resut, the rest Mueller matrix is presented by certain regular functions.