The Dynamics of the Transverse Optical Flux in Random Media

TL;DR

This paper investigates how the transverse optical flux and vortex dynamics evolve in correlated random media, highlighting the transition from paraxial to nonparaxial regimes and their effects on energy spectrum and vortex nucleation.

Contribution

It provides a detailed analysis of the optical flux, vortex behavior, and energy spectrum during the paraxial to nonparaxial transition in random media, employing Maxwell's equations and Green's functions.

Findings

Vortex number increases with the cube root of propagation distance.

A kink in nucleation rate occurs at maximum scintillation.

The energy spectrum evolves from paraxial to nonparaxial field characteristics.

Abstract

We study the evolution of the kinetic energy (or gradient norm) of an incident linearly polarized monochromatic wave propagating in correlated random media. We explore the optical flux transverse to the mean Poynting flux at the paraxial-nonparaxial (vectorial) transition along with vortex counting. Here, by paraxial-nonparaxial transition we mean a gradual loss of validity of the paraxial approximation such that it is necessary to solve Maxwell-consistently employing the dyadic Green's function. The vortex number appears to increase approximately with a cubic root of the propagation distance for sufficiently small correlation length. Furthermore, a kink appears in nucleation rate at the position of maximum scintillation upon increasing correlation length. A driven steady state is reached due to the filtering of evanescent waves upon propagation. Finally, we present the spectrum of the incompressible kinetic energy and how it evolves from the paraxial case to that of a (nonparaxial) random field.