Suppression of Interactions in Multimode Random Lasers in the Anderson Localized Regime

TL;DR

This paper develops a semiclassical theory showing that Anderson localization in strongly scattering random lasers suppresses modal interactions, resulting in noninteracting, long-lived localized lasing modes unaffected by pumping.

Contribution

It introduces a theory demonstrating that Anderson localization prevents interactions between modes in multimode random lasers, simplifying their analysis.

Findings

Anderson localization remains unaffected by nonlinearities.

Localization suppresses modal interactions in the laser.

Lasing modes are long-lived, localized, and independent of pumping.

Abstract

Understanding random lasing is a formidable theoretical challenge. Unlike conventional lasers, random lasers have no resonator to trap light, they are highly multimode with potentially strong modal interactions and they are based on disordered gain media, where photons undergo random multiple scattering. Interference effects notoriously modify the propagation of waves in such random media, but their fate in the presence of nonlinearity and interactions is poorly understood. Here, we present a semiclassical theory for multimode random lasing in the strongly scattering regime. We show that Anderson localization, a wave-interference effect, is not affected by the presence of nonlinearities. To the contrary, its presence suppresses interactions between simultaneously lasing modes. Using a recently constructed theory for complex multimode lasers, we show analytically how Anderson localization justifies a noninteracting, single-pole approximation. Consequently, lasing modes in a strongly scattering random laser are given by long-lived, Anderson localized modes of the passive cavity, whose frequency and wave profile does not vary with pumping, even in the multi-mode regime when mode overlap spatially.