Abstract

We propose a 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 ({mathscr{P}}{mathscr{T}}) symmetric system (i.e., coupled active-passive 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 increased 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.

Highlights

  • Achieving rapid development in integrated photonic circuits depends on the all-optical elements, which are essential for high-speed processing of light signals

  • Fan et al achieved the experiment of nonreciprocal light propagation with the Kerr and thermal nonlinearity in silicon microring resonators[22]

  • The strong nonlinearity required for nonreciprocal light propagation is not easy to obtain, especially for few-photon situations

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Summary

Introduction

Achieving rapid development in integrated photonic circuits depends on the all-optical elements, which are essential for high-speed processing of light signals. One can break time-reversal symmetry and design the nonreciprocal optical devices by time-dependent effects[5,6], unbalanced quantum coupling[7,8,9,10] or optical nonlinearity[11,12,13,14,15,16,17]. Based on two-level quantum emitters coupled to waveguides or microcavities, asymmetric light transmission has been experimentally observed[40,41,42,43] In these schemes, the breaking of the time-reversal symmetry relies on the chiral (direction dependent) light-matter interaction. Our scheme is based on the optical nonlinearity breaking time-reversal symmetry and the optical nonlinearity is induced by a single quantum emitter coupled to a microcavity beyond weak-excitation approximation. Via choosing proper parameters range, one can avoid the interference from the instability of output field intensity and obtain certain output intensity even for the strong disturbance of parameters

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