Light scattering by DNA structure due to phase transition

Modelling and numerical calculations of light scattering by the deoxyribonucleic acid (DNA) molecule were investigated using the transition matrix method at the phase transition region. In this model for a DNA molecule with helix structure, the electrical field was established and the transition matrix calculated for this field. Numerical computation of a simple cylindrical model, represented by adenine–thymine (A–T) and guanine–cytosine (G–C) formed with a lamellar-like helix, enabled important results to be obtained. These results were generalized for different molecular orientations with dielectric properties at the phase transition, which occurred due to the electric field changing. Finally, these results are associated with improved models for previous geometries.     

Light scattering by some nematic liquid crystals due to phase transitions

New computer modelling of light scattering and its propagation through liquid crystal has been presented using T-matrix method in the structural phase transition regions. Numerical aspects of light scattering process, which are based on numerically solving Maxwell's equations, were calculated for some nematic liquid crystals. Firstly, we described in detail T-matrix method for computing light scattering from nematic liquid crystals and presented results of benchmark computations for the considered model. We reported results of extensive calculations for polydisperse, randomly oriented rod-like multilayered systems (nematic liquid crystals). Our results are associated with light scattering by ferroelectric and ferroelastic materials.     

Fractal model of light scattering in biological tissue and cells

The K-distribution, widely used for investigation of fractal scattering in the atmosphere and from surfaces, is applied as a model for light propagation in biological tissue and cells. This leads to simple expressions for the scattering function, anisotropy function, phase function, reduced scattering coefficient, and scattering power. Compared with an alternative previously published model [Opt. Lett.30, 3051 (2005)], the range of allowable power laws is extended into the subfractal regime.     

Fractal mechanisms of light scattering in biological tissue and cells

We use fractal continuous random media to model visible and near-infrared light scattering by biological tissue and cell suspensions. The power law of the reduced scattering coefficient, the anisotropy factor of scattering, and the phase function are derived with good agreement with experimental results. Implications for spectroscopic tissue diagnosis are discussed.     

Liquid transport due to light scattering

Using experiments and theory, we show that light scattering by inhomogeneities in the index of refraction of a fluid can drive a large-scale flow. The experiment uses a near-critical, phase-separated liquid, which experiences large fluctuations in its index of refraction. A laser beam traversing the liquid produces a interface deformation on the scale of the experimental setup and can cause a liquid jet to form. We demonstrate that the deformation is produced by a scattering-induced flow by obtaining good agreements between the measured deformations and those calculated assuming this mechanism.     

Decoherence due to elastic Rayleigh scattering

We present theoretical and experimental studies of the decoherence of hyperfine ground-state superpositions due to elastic Rayleigh scattering of light off resonant with higher lying excited states. We demonstrate that under appropriate conditions, elastic Rayleigh scattering can be the dominant source of decoherence, contrary to previous discussions in the literature. We show that the elastic-scattering decoherence rate of a two-level system is given by the square of the difference between the elastic-scattering amplitudes for the two levels, and that for certain detunings of the light, the amplitudes can interfere constructively even when the elastic-scattering rates from the two levels are equal. We confirm this prediction through calculations and measurements of the total decoherence rate for a superposition of the valence electron spin levels in the ground state of 9Be+ in a 4.5?T magnetic field.     

Light scattering from colloids

This paper presents a review of light scattering results on static and dynamic properties of ordered colloidal suspensions of charged polystyrene particles and fractal colloidal aggregates. Our studies on static structure factor,S(Q), of ordered monodisperse colloidal suspensions and binary mixtures of particles with different particle diameters, measured by angle-resolved Rayleigh scattering will be discussed. This will include determination of bulk modulus using gravitational compression and observation of colloidal glass (inferred from splitting of the second peak inS(Q)). Dynamic light scattering, with real time analysis of scattered intensity fluctuations, is used to get information about Brownian dynamics of the particles. Recent advances in the field of light scattering from colloidal aggregates which show fractal geometry will also be discussed.     

Light scattering lineshape in opaque materials

The wavevector distribution excited by light scattering in opaque materials is calculated and compared to recently observed asymmetrical Brillouin lineshapes.     

Spin relaxation due to polar optical phonon scattering

Spin relaxation due to polar optical phonon scattering in semiconductors was investigated. The relaxation of the electron spin was found to increase with increasing the strength of the electric field. However, a high field completely depolarized the electron spin due to an increase of the spin precession frequency of the hot electrons, suggesting that high field transport conditions might not be desirable for spin-based technology with these semiconductors. It was also found that spin relaxation decreases with increasing moderately n-doping density or decreasing temperature. The results were discussed in comparison with the data available in the literature.     

Surface plasmon damping due to rough boundary scattering

The surface plasmon damping due to carriers scattering at the statistically rough (semiconductor-dialectric) interface is considered. The specular parameter and the integral relation are used as the boundary condition for a non-equilibrium part of the distribution function. There exist certain cases when the rough surface scattering of carriers is shown to play an important role in the surface plasmon damping.     

Light propagation and light scattering

A self-consistent theory is given for the propagation and scattering of light in a material medium. A generalized statement for the extinction theorem is obtained. To first order Yvon's result is recovered for the intensity of polarized scattered light.     

Light scattering from gas mixtures

The special features of the light scattering spectrum of disparate-mass gas mixtures are analyzed via the dispersion equation for the hydrodynamic modes.     

Light scattering at dielectric metasurfaces

“Photonic graphene” structures—submicron two-dimensional dielectric structures with a honeycomb lattice— are fabricated by laser lithography. The transition from the regime of light scattering by a metasurface to that of Laue diffraction at a two-dimensional photonic structure in the optical range is studied experimentally and theoretically. The optical diffraction patterns make it possible to determine the number of unit cells in a finite microstructured sample with the naked eye.     

Light scattering on ultrathin capillaries

In recent experiments, very low amplitudes of light scattering were reported for a tightly focused laser beam on a glass microcapillary. This result may be of great importance for single molecule detection in liquids. In the present paper, a theoretical study of the problem of light scattering of a focused laser beam on a cylindrical glass capillary is given. The numerical calculations are based on an exact electrodynamic treatment of the whole problem, including vector effects of the electromagnetic field of the laser beam. It is shown that under favorite conditions (inner and outer radius of the capillary, perfect adjustment of the laser beam) the intensity of the back-scattered light may be extremely low.     

血液的光散射特性

测定了不同血液样品(全血、红细胞、血浆)在可见光的吸收光谱,研究了He-Ne激光经过全血和红细胞的偏振度的变化,得出了人体血液中对可见光的吸收和散射主要来自红细胞的结论.     

Light scattering from magnons in ferromagnetic semiconductors

The effect of the electron-magnon interaction on the Raman scattering by magnons is discussed. It is shown that in addition to Loudon's spin-orbit coupling mechanism there is another, carrier-mediated, contribution to the Raman line. The frequency dependence of the resonant scattering is discussed and application to CdCr₂Se₄ is made.