Sergey V. Romanov

The effect of multiple scattering in disperse media on polarization characteristics of scattered light

The effect of scattering of different multiplicity on polarization characteristics of scattered light is studied by the Monte Carlo computer simulation technique. The scattering multiplicity distribution versus the direction of scattering and dimensions of the scattering system is obtained for monodisperse systems of spherical particles of different size. The angular dependences of the elements of the light-scattering matrix (LSM) are calculated. It is shown that in a system of spherical particles, specific features of the LSM structure associated with multiple scattering have much in common with similar features of the LSM in systems of nonspherical particles under conditions of single scattering. The angular dependences of the degree of depolarization of the scattered light are studied.

Investigation of Mueller matrices of anisotropic nonhomogeneous layers in application to an optical model of the cornea

We consider a system of anisotropic layers as an optical model of the eye cornea. Effective refraction indices for normally incident light are calculated with the assumption that each layer consists of closely packed uniform cylinders (fibrils). Jones matrix formalism is used to describe light propagation through the cornea. We calculate the Jones matrices from the experimentally measured Mueller matrices. Two algorithms are used for this purpose. The experiments have shown that ~20% of cornea area studied had the structure well described by the helical model proposed.

Relationships between Mueller matrix elements of real objects

The relationships between Mueller matrix elements are considered. The correctness of their application as a criterion for consistency of experimental data and for the estimation of depolarizing ability of real objects are analyzed. Experimental errors have been assessed by means of numerical simulation.

Influence of the multiple scattering on the polarization characteristic of bio-objects

In the work, behavior of the elements of light scattering matrix (LSM) is investigated during the process of aggregation of proteins of the eye lens. We consider a system of spherical scatterers as a model of the lens. The Monte-Carlo method is used to trace migration and scattering of photons in a medium. Light scattering on the particles is described by the Mie formulas. We investigate influence of the multiple scattering on spatial and polarization characteristics of the scattered laser light accounting for the given geometry of the experiment and obtain angular dependencies of the LSM elements. Also the angular dependencies of weights of different orders of scattering are obtained. It is shown, that for small particle systems the influence of multiple scattering has a maximum for the scattering angle equal to 90 degrees. Finally, we discuss light depolarization in the lens.

Nonlinear gain in one-dimensional quasi-periodic photon band-gap structure with Kerr effect

The gain in one-dimensional photonic band gap structure, containing active layers, is studied. Nonlinearity of the material, caused by Kerr effect, is taken into account. Nonlinear problem of wave transmission through nonlinear multilayered structure is solved using perturbation method. It is shown, that the gain in photonic band gap structure can be essentially enhanced at the photonic band gap edge in comparison with a bulk material having the same optical thickness.

Color of biotissues and artificial disperse systems under diffuse scattering of light

This paper deals with the problem of calculating the color characteristics of light scattered by disperse systems. Multiple scattering effects were taken into account.

Influence of shape and dimension of the cuvette on polarization characteristics of multiple scattered light

The Monte-Carlo method was used to study the effect of multiple light scattering on the mediums polarization characteristics. The influence of the scattering system parameters and experimental conditions on the results of LSM measurements were estimated. Calculation was performed for a monodisperse system of spherical particle. The scattering medium was enclosed in a spherical and a cylinder cells. The influence of cell wall thickness and light reflection at the medium-glass and glass-air interfaces was regarded. Various parameters of incident beam, cell diameter and scattering particles dimensions were employed for calculations.

Accuracy of polarization-sensitive optical coherence tomography of anisotropic layered biotissues

The inclusion of radiation polarization considerably extends the sensitivity and the potentials of optical coherence tomography. The recorded signals are however skewed by using wide-band light sources and polarization sensitive elements, as well as by frequency dispersion of the objects under study. It is essential for such layered system with spatial anisotropy as eye cornea and sclera.

Influence of multiple scattering on the results of measurements of light-scattering matrices

We have used, in our paper, the Monte Carlo method to study the multiple light scattering effect on the medium polarization characteristics. We have estimated the influence of a scattering system parameters and experimental conditions on the LSM measurement results. In our model a monodisperse system of spherical particle was used. The scattering substance was considered to be placed in a cylinder cell. Calculations were conducted for various parameters of incident beam, cell diameter and scattering particles dimensions. The calculations were performed for three values of particle diameters and different concentrations.

Influence of multiple light scattering on a photoacoustic signal

Photoacoustic spectroscopy is powerful method of investigation of absorption spectra of scattering media. This method was successfully applied for investigation of different biotissues. However the multiple scattering is essential in these media. It disturbs the output photoacoustic signals. So it is necessary take this phenomenon into account. The purpose of our work is to analyze the variations of photoacoustic signal versus the multiplicity of light scattering. Calculations are held for the model monodisperse spherical particles. Mie theory was applied to describe scattering by single spherical particle. The case of Gaussian profile beam was considered. Monte- Carlo method was used to calculate the photons trajectories in three dimension space. Such events as photon absorption, scattering and reflection from the sell walls was evaluated by random numbers with appropriate probability density. Angular dependence of probability density of the photon scattering is determined in terms of Mie theory for depolarized light. So we define coordinates of photons collision and absorption points. It enables us to determine the spatial distribution of the points of photon absorption, which depends on the shapes of scattering volume and beam profile. These calculations were made for the model of former elements of blood. It was shown that the multiple scattering varies the absorption profile of the beam. Since multiplicity of light scattering depends on the wavelength of incident light, then absorption spectrum is disturbed. The depth of light penetration into the medium appears to be essentially smaller in the case of short wavelengths.