Reciprocity principle and nonequivalence of counterpropagating modes in whistle-geometry ring lasers

Abstract

Greatly enhanced high-speed modulation performance has been recently predicted in numerical calculations for a novel injection-locking scheme involving a distributed Bragg reflector master laser monolithically integrated with a unidirectional whistle-geometry semiconductor micro ring laser. In this work, we confirm the unidirectionality of the whistle-geometry configuration through rigorous three-dimensional finite-difference time-domain (FDTD) simulation by showing a strong asymmetry in photon lifetimes between the two counter propagating modes. At the same time, we explain why this result does not violate the Helmholtz reciprocity principle.