Bistability and mode interaction in microlasers

TL;DR

This paper explores the conditions under which microlasers can exhibit bistable lasing behavior, demonstrating that microcavities are more conducive to bistability than bulk lasers, with theoretical and numerical validation.

Contribution

It provides a comprehensive analytical framework for understanding bistability in microlasers across different classes and confirms predictions with numerical simulations.

Findings

Bistability is possible in all classes of microlasers.

Microcavities enhance bistability conditions compared to bulk cavities.

Bistability persists even with non-degenerate modes in complex laser models.

Abstract

We investigate the possibility of bistable lasing in microcavity lasers as opposed to bulk lasers. To that end, the dynamic behavior of a microlaser featuring two coupled, interacting modes is analytically investigated within the framework of a semiclassical laser model, suitable for a wide range of cavity shapes and mode geometries. Closed-form coupled mode equations are obtained for all classes of laser dynamics. We show that bistable operation is possible in all of these classes. In the simplest case (class-A lasers) bistability is shown to result from an interplay between coherent (population-pulsation) and incoherent (hole-burning) processes of mode interaction. We find that microcavities offer better conditions to achieve bistable lasing than bulk cavities, especially if the modes are not degenerate in frequency. This results from better matching of the spatial intensity distribution of microcavity modes. In more complicated laser models (class-B and class-C) bistability is shown to persist for modes even further apart in frequency than in the class-A case. The predictions of the coupled mode theory have been confirmed using numerical finite-difference time-domain calculations.