Cavity optomechanics with stoichiometric SiN films

TL;DR

This paper demonstrates high-quality SiN films with exceptional mechanical and optical properties suitable for quantum optomechanics, including high Qmνm products and low optical absorption, enabling advanced cooling experiments.

Contribution

It introduces high-stress SiN films with record Qmνm products and low optical absorption, and develops an apparatus for cooling multiple mechanical modes.

Findings

Mechanical modes with Qmνm ≈ 2×10^{13} Hz achieved.

Optical absorption at 935 nm is significantly reduced.

Initial cooling of multiple mechanical modes demonstrated.

Abstract

We study high-stress SiN films for reaching the quantum regime with mesoscopic oscillators connected to a room-temperature thermal bath, for which there are stringent requirements on the oscillators' quality factors and frequencies. Our SiN films support mechanical modes with unprecedented products of mechanical quality factor $Q_m$ and frequency $\nu_m$ reaching $Q_{m} \nu_m \simeq2 \times 10^{13}$ Hz. The SiN membranes exhibit a low optical absorption characterized by Im$(n) \lesssim 10^{-5}$ at 935 nm, representing a 15 times reduction for SiN membranes. We have developed an apparatus to simultaneously cool the motion of multiple mechanical modes based on a short, high-finesse Fabry-Perot cavity and present initial cooling results along with future possibilities.