Diffusive to quasi-ballistic random laser: incoherent and coherent models

TL;DR

This paper compares incoherent and coherent models of random lasers to understand the transition from diffusive to quasi-ballistic regimes, showing that incoherent models can reliably predict thresholds and mode shapes.

Contribution

It demonstrates that incoherent diffusion and radiative transfer models align well with coherent wave models in predicting random laser thresholds and mode structures.

Findings

Incoherent and coherent models predict similar laser thresholds.

The shape of intensity distribution at threshold agrees across models.

Incoherent models offer useful analytical predictions for random laser behavior.

Abstract

We study the crossover between the diffusive and quasi-ballistic regimes of random lasers. In particular, we compare incoherent models based on the diffusion equation and the radiative transfer equation (RTE), which neglect all wave effects, with a coherent wave model for the random laser threshold. We show that both the incoherent and the coherent models predict qualitatively similar thresholds, with a smooth transition from a diffuse to a quasi-ballistic regime. The shape of the intensity distribution in the sample as predicted by the RTE model at threshold is also in good agreement with the coherent model. The approximate incoherent models thus provide useful analytical predictions for the threshold of random lasers as well as the shape of the random laser modes at threshold.