Loss-induced nonreciprocity

Xinyao Huang,Yong-Chun Liu,Cuicui Lu,Honggeng Tao,Chao Liang

doi:10.1038/s41377-021-00464-2

Abstract

Nonreciprocity is important in both optical information processing and topological photonics studies. Conventional principles for realizing nonreciprocity rely on magnetic fields, spatiotemporal modulation, or nonlinearity. Here we propose a generic principle for generating nonreciprocity by taking advantage of energy loss, which is usually regarded as harmful. The loss in a resonance mode induces a phase lag, which is independent of the energy transmission direction. When multichannel lossy resonance modes are combined, the resulting interference gives rise to nonreciprocity, with different coupling strengths for the forward and backward directions, and unidirectional energy transmission. This study opens a new avenue for the design of nonreciprocal devices without stringent requirements.

Highlights

Optical nonreciprocity, which prohibits a light field from returning along its original path after passing through an optical system in one direction, implying the breaking of the Lorentz reciprocity theorem, is crucially important for both fundamental studies and applied sciences[1,2,3]
It is obvious that loss breaks time-reversal symmetry, it is generally believed that loss cannot lead to optical nonreciprocity as a result of restricted time-reversal symmetry[2,3], in which the field amplitudes are reduced while the field ratios are conserved
Loss breaks the time-reversal symmetry according to the traditional definition of time reversal, it is commonly believed that in classical electrodynamics, only restricted time reversal is valid

Summary

Introduction

Optical nonreciprocity, which prohibits a light field from returning along its original path after passing through an optical system in one direction, implying the breaking of the Lorentz reciprocity theorem, is crucially important for both fundamental studies and applied sciences[1,2,3]. A number of approaches have been suggested for generating nonreciprocity, including the use of parity-time (PT)symmetric nonlinear cavities[9,10], spinning resonators[11,12], optomechanical interactions[13,14,15,16,17,18,19,20], cavity magnonic interactions[21], effective gauge fields[22,23], and the thermal motion of hot atoms[24,25] Despite these achievements, the basic principles for realizing optical nonreciprocity remain limited as a result of the time-reversal symmetry. This study paves the way for the observation of nonreciprocity and corresponding device design in lossy systems without stringent conditions, and provides opportunities for studying chiral and topological properties in systems with lossy coupling

Results

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Discussion