Coupled resonator-induced transparency in ring-bus-ring Mach-Zehnder interferometer

Abstract

This paper presents theoretical studies on the ring-bus-ring (RBR) resonator system, which consist of two resonators indirectly coupled through a center waveguide between them. By controlling the intercavity interaction and engineering the phase response through incorporation of RBR with Mach-Zehnder interferometer, we show that it is possible to generate a spectrum resembling electromagnetically induced transparency (EIT), which is qualitatively different compared to other existing EIT schemes. The transparency becomes sharper as the coupling strength between resonators is increased, with the background spectrum significantly reduced as a result of additional phase shift from indirect coupling. In addition, the EIT-like spectrum is generated out of low-finesse resonators, in contrast with existing EIT schemes where the resonator's finesse is required to be high. Comparisons with finite-difference-time-domain simulation show fairly a good agreement with analytical formulations.