Loss-induced suppression and revival of lasing

TL;DR

This paper demonstrates how exceptional points in coupled microresonators can be used to control laser behavior, turning loss into gain, and enabling the revival of lasing after suppression.

Contribution

It introduces a novel approach to manipulate loss in lasers by steering system parameters near exceptional points, showing loss-induced suppression and revival of lasing.

Findings

Loss can suppress laser action below a critical point.

Lasing recovers beyond the critical loss threshold.

Exceptional points enable counterintuitive loss management.

Abstract

Controlling and reversing the effects of loss are major challenges in optical systems. For lasers losses need to be overcome by a sufficient amount of gain to reach the lasing threshold. We show how to turn losses into gain by steering the parameters of a system to the vicinity of an exceptional point (EP), which occurs when the eigenvalues and the corresponding eigenstates of a system coalesce. In our system of coupled microresonators, EPs are manifested as the loss-induced suppression and revival of lasing. Below a critical value, adding loss annihilates an existing Raman laser. Beyond this critical threshold, lasing recovers despite the increasing loss, in stark contrast to what would be expected from conventional laser theory. Our results exemplify the counterintuitive features of EPs and present an innovative method for reversing the effect of loss.