High-reflectivity, high-Q micromechanical membranes via guided resonances for enhanced optomechanical coupling

TL;DR

This paper demonstrates that guided resonances in photonic crystal membranes can significantly enhance optical reflectivity without compromising mechanical quality, advancing optomechanical systems toward quantum ground state cooling.

Contribution

It introduces a method to increase membrane reflectivity using Fano-type guided resonances, maintaining high mechanical Q factors, thus improving optomechanical coupling in membrane systems.

Findings

Reflectivity increased by approximately 4 times at 1064 nm.

Mechanical Q factors remained high at around 5 million.

Potential for ground state cooling and quantum effects observation.

Abstract

Using Fano-type guided resonances (GRs) in photonic crystal (PhC) slab structures, we numerically and experimentally demonstrate optical reflectivity enhancement of high-Q SiNx membrane-type resonators used in membrane-in-the-middle optomechanical (OM) systems. Normal-incidence transmission and mechanical ringdown measurements of 50-nm-thick PhC membranes demonstrate GRs near 1064 nm, leading to a ~ 4\times increase in reflectivity while preserving high mechanical Q factors of up to ~ 5 \times 10^6. The results would allow improvement of membrane-in-the-middle OM systems by virtue of increased OM coupling, presenting a path towards ground state cooling of such a membrane and observations of related quantum effects.