Strong Interactions in Multimode Random Lasers

TLDR

Diffusive random lasers lack resonators and sharp resonances, making them challenging for conventional laser theory, and they typically emit multiple wavelengths. The authors develop a rigorous theory for diffusive random lasers. The theory provides lasing spectra, internal fields, and output intensities. Modal interactions in multimode DRLs are extremely strong, producing a uniformly spaced frequency spectrum that matches recent experiments.

Abstract

Unlike conventional lasers, diffusive random lasers (DRLs) have no resonator to trap light and no high-Q resonances to support lasing. Because of this lack of sharp resonances, the DRL has presented a challenge to conventional laser theory. We present a theory able to treat the DRL rigorously and provide results on the lasing spectra, internal fields, and output intensities of DRLs. Typically DRLs are highly multimode lasers, emitting light at a number of wavelengths. We show that the modal interactions through the gain medium in such lasers are extremely strong and lead to a uniformly spaced frequency spectrum, in agreement with recent experimental observations.