Quasibound states in the continuum in photonic-crystal-based optomechanical microcavities

TL;DR

This paper explores simplified photonic-crystal microcavities with quasi-bound states in the continuum, aiming to achieve high optical quality factors by reducing radiative losses for advanced optomechanical applications.

Contribution

It demonstrates that a suspended photonic-crystal slab facing a distributed Bragg reflector can realize a quasi-bound state in the continuum with high optical quality factors, simplifying previous designs.

Findings

Optical quality factors exceeding 10^5 predicted.

Radiative loss can be minimized to material absorption.

Simplified cavity design feasible for experimental realization.

Abstract

We present a detailed study of mechanically compliant, photonic-crystal-based microcavities featuring a quasi-bound state in the continuum. Such systems have recently been predicted to reduce the optical loss in Fabry-Perot-type optomechanical cavities. However, they require two identical photonic-crystal slabs facing each other, which poses a considerable challenge for experimental implementation. We investigate how such an ideal system can be simplified and still exhibit a quasi-bound state in the continuum. We find that a suspended photonic-crystal slab facing a distributed Bragg reflector realizes an optomechanical system with a quasi-bound state in the continuum. In this system, the radiative cavity loss can be eliminated to the extent that the cavity loss is dominated by dissipative loss originating from material absorption only. These proposed optomechanical cavity designs are predicted to feature optical quality factors in excess of 10^5.