Yalong Gu

Scintillation of Nonuniformly Polarized Beams in Atmospheric Turbulence

We demonstrate, through numerical simulations, that an appropriately chosen nonuniformly polarized coherent optical field can have appreciably smaller scintillation than comparable beams of uniform polarization. This results from the fact that a nonuniformly polarized field acts as an effective two-mode partially coherent field. The results described here are of direct relevance to the development of free-space optical communication systems.

Scintillation of pseudo-Bessel correlated beams in atmospheric turbulence

The concept of pseudo-Bessel correlated beams is introduced, and their scintillation properties on propagation through turbulence are investigated. By using the Rytov approximation, the scintillation index of pseudo-Bessel correlated beams is formulated in weak turbulence. The study of scintillation is extended into strong turbulence by numeric simulations. It is shown that by choosing an appropriate coherence parameter, pseudo-Bessel correlated beams have lower scintillation than comparable fully coherent beams in both weak and strong turbulence. In addition, the configuration of pseudo-Bessel correlated beams is modified by adding a horizontal beamlet; the scintillation properties of these modified beams are also discussed.

Reduction of turbulence-induced scintillation by nonuniformly polarized beam arrays

We have explored a method to reduce turbulence-induced scintillation by using an incoherent beam array composed of beamlets with nonuniform polarization. It is shown that significant scintillation reduction of such an incoherent beam array can be obtained by using nonuniformly polarized beamlets whose scintillation properties are optimized.

Statistics of optical vortex wander on propagation through atmospheric turbulence

The transverse position of an optical vortex on propagation through atmospheric turbulence is studied. The probability density of the optical vortex position on a transverse plane in the atmosphere is formulated in weak turbulence by using the Born approximation. With these formulas, the effect of aperture averaging on topological charge detection is investigated. These results provide quantitative guidelines for the design of an optimal detector of topological charge, which has potential application in optical vortex communication systems.

Coherence converting plasmonic hole arrays

Simulations are presented that demonstrate that the global state of spatial coherence of an optical wavefield can be altered on transmission through an array of subwavelength-sized holes in a metal plate that supports surface plasmons. It is found that the state of coherence of the emergent field strongly depends on the separation between the holes and their scattering strength. Our findings suggest that subwavelength hole arrays on a metal film can be potentially employed as a plasmon-assisted coherence converting device, useful in modifying the directionality, spectrum, and polarization of the transmitted wave.

Phase singularities, correlation singularities, and conditions for complete destructive interference.

A previously derived condition for the complete destructive interference of partially coherent light emerging from a trio of pinholes in an opaque screen is generalized to the case when the coherence properties of the field are asymmetric. It is shown by example that the interference condition is necessary, but not sufficient, and that the existence of complete destructive interference also depends on the intensity of light emerging from the pinholes and the system geometry; more general conditions for such interference are derived. The phase of the wave field exhibits both phase singularities and correlation singularities, and a number of nonintuitive situations in which complete destructive interference occurs are described and explained.

Use of Nonconventional Incoherent Beam Arrays for Reduction of Turbulence-induced Scintillation

General guidelines for use of nonconventional incoherent beam arrays in scintillation reduction are explored; with these a new beam class is considered and the scintillation of the corresponding incoherent beam array is significantly reduced.

Topological Reactions of Correlation Vortices

The topological reactions of correlation vortices are investigated. They suggest the possible use of correlation vortices as a probe of the statistical properties of a field or a medium.

Spatial Coherence Modulation with a Subwavelength Plasmonic Hole Array

We have investigated the spatial coherence properties of light on transmission through a subwavelength metallic hole array which supports surface plasmons. It shows that the modulation of such properties strongly depends on the array geometry.

Reduction of Turbulence-induced Scintillation by Nonuniformly Polarized Beam Arrays

We have investigated scintillation properties of nonuniformly polarized beam arrays. It is shown that turbulence-induced scintillation can be significantly reduced by such arrays whose nonuniformly polarized beamlets have optimized scintillation properties.