2D photonic-crystal optomechanical nanoresonator

TL;DR

This paper reports the optical design and optimization of a 2D photonic-crystal optomechanical nanoresonator using a suspended InP membrane, achieving high reflectivity and a compact microcavity for probing mechanical motion.

Contribution

It introduces a numerically optimized 2D photonic-crystal grating on InP for high-reflectivity microcavities in optomechanics.

Findings

Reflectivity >99.8% over 50 nm bandwidth

Microcavity waist smaller than 10 μm with finesse ~200

Successful probing of nanomembrane Brownian motion

Abstract

We present the optical optimization of an optomechanical device based on a suspended InP membrane patterned with a 2D near-wavelength grating (NWG) based on a 2D photonic-crystal geometry. We first identify by numerical simulation a set of geometrical parameters providing a reflectivity higher than 99.8 % over a 50-nm span. We then study the limitations induced by the finite value of the optical waist and lateral size of the NWG pattern using different numerical approaches. The NWG grating, pierced in a suspended InP 265 nm-thick membrane, is used to form a compact microcavity involving the suspended nano-membrane as end mirror. The resulting cavity has a waist size smaller than 10 $\mu$m and a finesse in the 200 range. It is used to probe the Brownian motion of the mechanical modes of the nanomembrane.