Optomechanical Anti-lasing with Infinite Group Delay at a Phase Singularity

TL;DR

This paper demonstrates how optomechanical systems can exhibit phase singularities that lead to infinite group delay or advance, enabling control over light propagation speed.

Contribution

It experimentally reveals the occurrence of phase singularities and infinite group delay in an optomechanical system, advancing understanding of light-matter interactions at critical coupling.

Findings

Observation of simultaneous coherent perfect absorption and anti-lasing.

Detection of an abrupt π-phase transition at the singularity.

Demonstration of a transition from infinite group delay to advance.

Abstract

Singularities that symbolize abrupt changes and exhibit extraordinary behavior are of broad interest. We experimentally study optomechanically induced singularities in a compound system consisting of a three-dimensional aluminum superconducting cavity and a metalized high-coherence silicon nitride membrane resonator. Mechanically-induced coherent perfect absorption and anti-lasing occur simultaneously under a critical optomechanical coupling strength. Meanwhile, the phase around the cavity resonance undergoes an abrupt $\pi$-phase transition, which further flips the phase slope in the frequency dependence. The observed infinite-discontinuity in the phase slope defines a singularity, at which the group velocity is dramatically changed. Around the singularity, an abrupt transition from an infinite group advance to delay is demonstrated by measuring a Gaussian-shaped waveform propagating. Our experiment may broaden the scope of realizing extremely long group delays by taking advantage of singularities.