Correlations in Transmission of Light through a Disordered Amplifying Medium

TL;DR

This paper investigates how light transmission correlations behave in a strongly scattering, amplifying medium, revealing unique features such as oscillations, absence of memory effect, and enhanced mode interactions near lasing threshold.

Contribution

It provides a detailed analysis of angular, frequency, and time correlation functions in disordered amplifying media, highlighting differences from elastic scattering and effects near lasing threshold.

Findings

Angular correlation exhibits power-law decay and oscillations.

No memory effect observed in the angular correlation.

Correlation scales change significantly near the lasing threshold.

Abstract

The angular and frequency correlation functions of the transmission coefficient for light propagation through a strongly scattering amplifying medium are considered. It is found that just as in the case of an elastic scattering medium the correlation function consists of three terms. However, the structure of the terms is rather different. Angular correlation has a power-law decay and exhibits oscillations. There is no "memory effect" as in the case of an elastic medium. Interaction between diffusion modes is strongly enhanced near the lasing threshold. Frequency correlation scale decreases close to the lasing threshold. We also consider time correlations of the transmission in the case of nonstationary inhomogeneities. We find short- and long-range time correlations. The scale of the short-range correlation decreases, while the long-range correlation scale becomes infinite near the threshold.