Kerr-type nonlinear optical isolators bypassing dynamic reciprocity

TL;DR

This paper introduces a novel approach to overcome dynamic reciprocity in Kerr-type nonlinear optical isolators, enabling backward signal isolation despite strong forward signals, using velocity-selective nonlinearity in an atomic cavity system.

Contribution

It proposes and experimentally demonstrates a new method to bypass dynamic reciprocity in passive Kerr-type optical isolators, advancing their practical implementation.

Findings

Successful experimental isolation of backward signals with strong forward signals

Agreement between experimental results and theoretical simulations

Advancement towards practical Kerr-type passive optical isolators

Abstract

Magnetic-free optical isolators are critical components for the realization of integrated optical systems. The underlying physics of passive nonlinear optical isolators is not solely about breaking the Lorentz reciprocity without requiring any external bias. Indeed, one major obstacle to the operation of Kerr-type nonlinear optical isolators was found to be the so-called dynamic reciprocity, of which the serious outcome is that a backward signal cannot be isolated in the presence of a forward strong signal. In this work, we advocate the novel concept of velocity-selective nonlinearity to bypass such dynamic reciprocity. Using a proof-of-principle platform with warm rubidium atoms in an asymmetric cavity, we experimentally achieve the isolation of a backward signal in the presence of a strong forward signal, with experimental observations in agreement with our theoretical simulations. This work has thus made one essential step towards functioning Kerr-type passive optical isolators.