Inverse Vernier Effects in Coupled Lasers

TL;DR

This paper investigates the Vernier effect in coupled laser systems, revealing conditions for both enhancement and suppression of lasing modes, and introduces the inverse Vernier effect linked to detuning-dependent Q-spoiling.

Contribution

It demonstrates the inverse Vernier effect in active laser systems and explains its origin as detuning-dependent Q-spoiling, expanding understanding of mode control in coupled lasers.

Findings

Supermodes can have increased thresholds and be suppressed.

Inverse Vernier effect can lead to single-mode lasing.

Relation to exceptional points in coupled lasers.

Abstract

In this report we study the Vernier effect in coupled laser systems consisting of two cavities. We show that depending on the nature of their coupling, not only can the "supermodes" formed at the overlapping resonances of the coupled cavities have the lowest thresholds and lase first as previously suggested, leading to a manifestation of the typical Vernier effect now in an active system; these supermodes can also have increased thresholds and are hence suppressed, which can be viewed as an inverse Vernier effect. We attribute this effect to detuning-dependent Q-spoiling, and it can lead to an increased free spectrum range and possibly single-mode lasing, which may explain the experimental findings of several previous work. We illustrate this effect using two coupled micro-ring cavities and a micro-ring cavity coupled to a slab cavity, and we discuss its relation to the existence of exceptional points in coupled lasers.