Mode Repulsion and Mode Coupling in Random Lasers

TL;DR

This paper investigates how lasing modes in random media interact, showing that gain properties influence mode repulsion and coupling, which can lead to synchronization or anti-phased oscillations.

Contribution

It provides experimental and theoretical insights into mode interactions, revealing mechanisms of mode repulsion and coupling in different gain media.

Findings

Cross gain saturation causes spatial mode repulsion in homogeneous media.

Spectral mode repulsion occurs in inhomogeneous media.

Weak coupling leads to mode synchronization, strong coupling causes anti-phased oscillations.

Abstract

We studied experimentally and theoretically the interaction of lasing modes in random media. In a homogeneously broadened gain medium, cross gain saturation leads to spatial repulsion of lasing modes. In an inhomogeneously broadened gain medium, mode repulsion occurs in the spectral domain. Some lasing modes are coupled through photon hopping or electron absorption and reemission. Under pulsed pumping, weak coupling of two modes leads to synchronization of their lasing action. Strong coupling of two lasing modes results in anti-phased oscillations of their intensities.