Zhangrong Mei

Random sources generating ring-shaped beams

Two classes of scalar, stochastic sources are introduced, each capable of producing far fields with intensities forming rings. Although the Bessel-Gaussian and the Laguerre-Gaussian Schell-model sources are described by two different math models, the behavior of their degrees of coherence and, hence, the shapes of their far fields are qualitatively similar. The new beams are of importance for optical methods of particle manipulation.

Cosine-Gaussian Schell-model sources

We introduce a new class of partially coherent sources of Schell type with cosine-Gaussian spectral degree of coherence and confirm that such sources are physically genuine. Further, we derive the expression for the cross-spectral density function of a beam generated by the novel source propagating in free space and analyze the evolution of the spectral density and the spectral degree of coherence. It is shown that at sufficiently large distances from the source the degree of coherence of the propagating beam assumes Gaussian shape while the spectral density takes on the dark-hollow profile.

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.

Propagation of cosine-Gaussian-correlated Schell-model beams in atmospheric turbulence.

A stochastic beam generated by a recently introduced source of Schell type with cosine-Gaussian spectral degree of coherence is shown to possess interesting novel features on propagation in isotropic and homogeneous atmospheric turbulence with general non-Kolmogorov power spectrum. It is shown that while at small distances from the source the beams intensity exhibits annular profile with adjustable area of the dark region, the center disappears at sufficiently large distances and the beams intensity tends to Gaussian form. Hence the 3D bottle beam is produced by the cumulative effect of the random source and the atmosphere. The distances at which the on-axis beam intensity has local minima and maxima are shown to have analytic dependence on the source and the atmospheric parameters. And the influence of the fractal constant of the atmospheric power spectrum and refractive-index structure constant on beam characteristics is analyzed in depth. The novel double-cycle qualitative change in the degree of coherence is shown to occur on atmospheric propagation which was not previously known for any other beams.

Electromagnetic non-uniformly correlated beams in turbulent atmosphere

Electromagnetic random beams with non-uniform source correlations have been recently shown to develop, on propagation in free space, the regions in transverse cross-sections where the degree and the state of polarization can significantly differ from those beyond that region. The size of the region and the values of polarimetric properties in it can be fully controlled from the source plane. In this paper the influence of a random isotropic medium on such beams is shown to suppress the effect in several ways, in particular by shifting the location of the region back to the axis.

Electromagnetic cosine-Gaussian Schell-model beams in free space and atmospheric turbulence

A recently introduced class of scalar cosine-Gaussian Schell-Model [CGSM] beams is generalized to electromagnetic theory. The realizability conditions and the beam conditions on the source parameters are derived. Analytical formulas for the cross-spectral density matrix elements of the electromagnetic cosine-Gaussian Schell-model [EM CGSM] beams propagating in isotropic random medium are derived. It is found that the EM CGSM beams possess single-ring or double-ring intensity profiles, depending of source parameters. As two examples, the statistical characteristics of the EM CGSM beams propagating in free space and non-Kolmogorov turbulent atmosphere are studied numerically. The effects of the fractal constant of the atmospheric spectrum and the refractive-index structure constant on such characteristics are analyzed in detail.

Gaussian Schell-model arrays

We introduce a novel class of planar, quasi-homogeneous Schell-model source for producing far fields with optical lattice average intensity patterns and derive the corresponding beam conditions. The array dimension, lobes intensity profile, and periodicity of the optical lattice can be flexibly tuned by changing the correlation parameters of the source field. It is also found that, with an appropriate choice of the source parameters, the radiant intensity may possess flat-topped intensity patterns.

Random light scattering by collections of ellipsoids.

Theory of weak scattering of random optical fields from deterministic collections of particles with soft ellipsoidal scattering potentials of arbitrary shapes and orientations is developed. Far-field intensity distribution produced on scattering is shown to be influenced by source correlation properties as well as by a number, shapes and orientations of scatterers. The theory extends previous results on scattering from collections of spheres with soft Gaussian potentials and is applicable to analysis of a wide range of media including blood cells.

Alternating series of cross-spectral densities

We establish a sufficient condition under which the alternation series of cross-spectral densities (CSD) constitutes a valid CSD. Using such a condition, we introduce a novel class of multi-sinc Schell-model sources with circular and Cartesian symmetries. It is demonstrated that far fields produced by the new sources carry interesting characteristics, being adjustable multi-rings and lattice patterns.

Products of Schell-model cross-spectral densities

The condition under which a product of two cross-spectral densities (CSD) constitutes a valid correlation function is established. The results are obtained for the CSDs of two one-dimensional, scalar Schell-model sources, but can be readily generalized to other situations. It is shown via a number of numerical examples how new source classes of Schell-model type and the beam-like fields they radiate can be designed.