Zhisong Tong

Nonuniformly correlated light beams in uniformly correlated media

The behavior of scalar beams with nonuniform correlations in isotropic random media is investigated. An example illustrates the fact that the off-axis intensity maximum formed in the transverse cross section of a nonuniformly correlated beam on propagation in free space is suppressed when it passes at sufficiently large distances from its source through the isotropic turbulent atmosphere.

Electromagnetic nonuniformly correlated beams

A class of electromagnetic sources with nonuniformly distributed field correlations is introduced. The conditions on source parameters guaranteeing that the source generates a physical beam are derived. It is shown that the new sources are capable of producing beams with polarization properties that evolve on propagation in a manner much more complex compared to the well-known electromagnetic Gaussian Schell-model 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.

Beyond the classical Rayleigh limit with twisted light

It is shown that twisted stochastic light can serve as illumination that may produce images with a resolution overcoming the Rayleigh limit by an order of magnitude. This finding is illustrated for an isoplanatic axially symmetric system with low angular aperture and twisted scalar Gaussian Schell-model illumination.

Stochastic Electromagnetic Beams in Positive-and Negative-Phase Materials

Theoretical analysis of interaction of stochastic electromagnetic beamlike fields with positive- and negative-phase materials suggests that suitable combinations of such materials can serve as media where spectral, coherence, and polarization properties of beams can self-reconstruct.

Technique for interaction of optical fields with turbulent medium containing particles

We develop a method for transmission of stochastic fields through turbulent media (atmosphere, ocean, biotissues) containing randomly distributed particles. The method is based on the angular spectrum representation of stochastic, statistically stationary, scalar fields, the Rytov perturbation series for propagation in weakly fluctuating media, and the first Born approximation for weak scattering from particulate media. The results for transmission of the deterministic (laser) field may be obtained from our general results as a limiting case.

Method for tracing the position of an alien object embedded in a random particulate medium

We have developed a new technique based on light scattering experiments for tracing an alien particle with deterministic potential in a random collection of particles. We have shown that, via a sequence of measurements of light scattered to a far field of a scattering collection, it is possible to locate the center of the alien particle. The analysis of the stability of reconstruction is provided, and it is demonstrated via simulations that the results are stable for sufficiently large wavelength of the incident light and in cases when the size of the alien particle is comparable with the size of the typical particle in the collection.

Degree of coherence in curvilinear coordinates and its application to scattering.

In the traditional treatment of the spectral degree of coherence, the Cartesian coordinate system is deployed to describe the electromagnetic field. In the description of the far field scattered from random media, however, the spherical polar coordinates system is more suitably used due to the fields outgoing spherical form. We hence derive the expression for the spectral degree of coherence in the spherical polar coordinates system. An example of one polychromatic plane wave scattered by a collection of identical particles is given.

Momentum of light scattered from collections of particles

The angular dependence of the momentum flow in a polychromatic plane wave scattered from deterministic and random collections of particles is determined as a function of individual and collective properties of particles.

Electromagnetic scattering from biological tissue

Based on the mathematical models of the experimentally fitted spectrum of index inhomogeneities, we analyze the electromagnetic field scattered from biological tissue. The resulting cross-spectral density matrices are expressed in spherical polar coordinates and the two-dimensional definition of polarization could be used. The results show that the polarization characteristics of the far scattered field depend closely on the types of the tissue.