Nonreciprocity light propagation in coupled microcavities system beyond weak-excitation approximation

TL;DR

This paper introduces a scheme for nonreciprocal light propagation in coupled microcavities with a quantum emitter, achieving high isolation and controllable directionality beyond weak-excitation limits.

Contribution

It demonstrates a method to enhance optical nonlinearity and achieve non-lossy nonreciprocal light propagation using PT-symmetric coupled cavities with quantum emitters.

Findings

Achieves high isolation ratio in nonreciprocal light propagation.

Shows nonreciprocity is robust against optical bistability effects.

Enables switching of propagation direction by parameter tuning.

Abstract

We propose an alternative scheme for nonreciprocal light propagation in two coupled cavities system, in which a two-level quantum emitter is coupled to one of the optical microcavities. For the case of parity-time (\textrm{PT}) system (i.e., active-passive coupled cavities system), the cavity gain can significantly enhance the optical nonlinearity induced by the interaction between a quantum emitter and cavity field beyond weak-excitation approximation. The giant optical nonlinearity results in the non-lossy nonreciprocal light propagation with high isolation ratio in proper parameters range. In addition, our calculations show that nonreciprocal light propagation will not be affected by the unstable output field intensity caused by optical bistability and we can even switch directions of nonreciprocal light propagation by appropriately adjusting the system parameters.