Integrated optomechanical arrays of two high reflectivity SiN membranes

TL;DR

This paper reports the fabrication and characterization of integrated arrays of two high-reflectivity SiN membranes, enabling enhanced optomechanical coupling and paving the way for multi-mode quantum experiments.

Contribution

The authors present a novel monolithic fabrication of dual high-reflectivity SiN membrane arrays with high finesse, overcoming previous alignment challenges in multi-element cavity optomechanics.

Findings

Achieved finesse up to 220 in 200 μm Fabry-Pérot cavities.

Observed increased optomechanical coupling compared to single membranes.

Predicted potential for reaching single-photon strong coupling regime.

Abstract

Multi-element cavity optomechanics constitutes a direction to observe novel effects with mechanical resonators. Several exciting ideas include superradiance, increased optomechanical coupling, and quantum effects between distinct mechanical modes among others. Realizing these experiments has so far been difficult, because of the need for extremely precise positioning of the elements relative to one another due to the high-reflectivity required for each element. Here we overcome this challenge and present the fabrication of monolithic arrays of two highly reflective mechanical resonators in a single chip. We characterize the optical spectra and losses of these 200 $\mu$m-long Fabry-P\'{e}rot interferometers, measuring finesse values of up to 220. In addition, we observe an enhancement of the coupling rate between the cavity field and the mechanical center-of-mass mode compared to the single membrane case. Further enhancements in coupling with these devices are predicted, potentially reaching the single-photon strong coupling regime, giving these integrated structures an exciting prospect for future multi-mode quantum experiments.