Perfect nonreciprocity by loss engineering

TL;DR

This paper introduces a loss engineering approach to achieve perfect nonreciprocity in optical transmission, enabling lossless unidirectional flow with high contrast by controlling energy losses and interference effects.

Contribution

It presents a generic method to realize lossless nonreciprocal transmission through energy loss manipulation, achieving high contrast and broadband operation.

Findings

Achieves 100% nonreciprocity contrast with zero insertion loss.

Maintains nonreciprocity over a wide bandwidth.

Demonstrates robustness against loss variations.

Abstract

Realization of nonreciprocal transmission with low insertion loss and high contrast simultaneously is in great demand for one-way optical communication and information processing. Here we propose a generic approach to achieving perfect nonreciprocity that allows lossless unidirectional transmission by engineering energy losses. The loss of the intermediate mode induces a phase lag impinging on the indirect channel for energy transmission, which does not depend on the energy transmission direction. When the direct transmission channel coexists with the indirect lossy transmission channel, the dual-channel interference can be tuned to be destructive simultaneously for backward transmission from the rightmost mode to the leftmost mode, and for forward transmission from the leftmost mode to the intermediate mode. The former interference outcome corresponds to 100% nonreciprocity contrast, and the latter guarantees zero insertion loss for forward transmission. Additionally, our scheme also allows a nonreciprocity response over a wide bandwidth by increasing the losses while keeping perfect nonreciprocity at resonance. The robustness against loss indicates that our scheme is advantageous in the implementation of nonreciprocal optical devices with high performance.