Nonreciprocity and magnetic-free isolation based on optomechanical interactions

TL;DR

This paper demonstrates how optomechanical interactions can be used to achieve nonreciprocal optical transmission and isolation without magnetic fields, using a silica microtoroid resonator to realize up to 10 dB isolation at telecom wavelengths.

Contribution

The work establishes minimal conditions for nonreciprocity in optomechanical systems and experimentally demonstrates optical isolation and nonreciprocal amplification in a microtoroid resonator.

Findings

Achieved up to 10 dB optical isolation at telecom wavelengths

Demonstrated nonreciprocal parametric amplification

Nonreciprocal transmission preserved for nondegenerate modes

Abstract

Photonic nonreciprocal components, such as isolators and circulators, provide highly desirable functionalities for optical circuitry. This motivates the active investigation of mechanisms that break reciprocity, and pose alternatives to magneto-optic effects in on-chip systems. In this work, we use optomechanical interactions to strongly break reciprocity in a compact system. We derive minimal requirements to create nonreciprocity in a wide class of systems that couple two optical modes to a mechanical mode, highlighting the importance of optically biasing the modes at a controlled phase difference. We realize these principles in a silica microtoroid optomechanical resonator and use quantitative heterodyne spectroscopy to demonstrate up to 10 dB optical isolation at telecom wavelengths. We show that nonreciprocal transmission is preserved for nondegenerate modes, and demonstrate nonreciprocal parametric amplification. These results open a route to exploiting various nonreciprocal effects in optomechanical systems in different electromagnetic and mechanical frequency regimes, including optomechanical metamaterials with topologically non-trivial properties.