Breaking Reciprocity in a non-Hermitian Photonic Coupler with Saturable Absorption

TL;DR

This paper investigates how saturable absorption and exceptional points in non-Hermitian photonic waveguides can break reciprocity, enabling broadband nonreciprocal devices for high-speed on-chip applications.

Contribution

It introduces a new passive non-resonant nonreciprocal device leveraging nonlinear saturable absorption and exceptional points, with analytical and numerical validation.

Findings

Analytical and semi-analytical transmission results

Validated nonreciprocal intensity range

Potential for broadband on-chip nonreciprocal operation

Abstract

We study the breaking of reciprocity in non-Hermitian coupled photonic waveguides by the simultaneous action of the nonlinear effect of saturable absorption, and the presence of exceptional points. The nonlinear response of such a system is studied in depth, giving physical insight into the operational principles and fundamental limitations, while producing analytical and semi-analytical results for the transmission and nonreciprocal intensity range. We numerically validate the theoretical results and assess important performance metrics for the nonreciprocal operation of such a device. This novel class of passive non-resonant devices can offer on-chip broadband nonreciprocal operation, making them potentially very important for high-speed applications.