Interaction-induced mode switching in steady-state microlasers

TL;DR

This paper reveals how strong modal interactions in microlasers can cause one lasing mode to switch off another through cross-gain saturation, offering a new mechanism for optical switching.

Contribution

It introduces the concept of interaction-induced mode switching (IMS) in steady-state microlasers and provides an analytic criterion for its occurrence based on modal interactions.

Findings

IMS occurs via negative power slope due to modal interactions.

A simple analytic criterion predicts IMS based on interaction coefficients.

Pump profile variation can induce IMS even when fixed profiles do not.

Abstract

We demonstrate that due to strong modal interactions through cross-gain saturation, the onset of a new lasing mode can switch off an existing mode via a negative power slope. In this process of interaction-induced mode switching (IMS) the two involved modes maintain their identities, i.e. they do not change their spatial field patterns or lasing frequencies. For a fixed pump profile, a simple analytic criterion for the occurrence of IMS is given in terms of their self- and cross-interaction coefficients and non-interacting thresholds, which is verified for the example of a two-dimensional microdisk laser. When the spatial pump profile is varied as the pump power is increased, IMS can be induced even when it would not occur with a fixed pump profile, as we show for two coupled laser cavities. Our findings apply to steady-state lasing and are hence different from dynamical mode switching or hopping. IMS may have potential applications in robust and flexible all-optical switching.