Mechanically Compliant Grating Reflectors for Optomechanics

TL;DR

This paper introduces silicon nitride membrane gratings with high reflectivity and quality factors, enabling advanced optomechanical experiments like high-finesse cavities and self-oscillations.

Contribution

It presents a novel mechanically compliant grating reflector with high reflectivity and quality factor, simplifying fabrication for optomechanical systems.

Findings

Reflectivity up to 99.4% achieved

Mechanical quality factor Q as high as 7.8×10^5

Constructed a high-finesse Fabry-Perot cavity with F=1200

Abstract

We demonstrate micromechanical reflectors with a reflectivity as large as 99.4% and a mechanical quality factor Q as large as 7.8*10^5 for optomechanical applications. The reflectors are silicon nitride membranes patterned with sub-wavelength grating structures, obviating the need for the many dielectric layers used in conventional mirrors. We have employed the reflectors in the construction of a Fabry-Perot cavity with a finesse as high as F=1200, and used the optical response to probe the mechanical properties of the membrane. By driving the cavity with light detuned to the high-frequency side of a cavity resonance, we create an optical antidamping force that causes the reflector to self-oscillate at 211 kHz.