Cavity optomechanics with Si3N4 membranes at cryogenic temperatures

TL;DR

This paper presents a cryogenic cavity-optomechanical system using Si3N4 membranes that achieves near-ground-state cooling of mechanical modes, highlighting challenges and solutions related to thermal noise at low temperatures.

Contribution

It introduces a novel cryogenic cavity-optomechanical platform with high-Q Si3N4 membranes capable of cooling mechanical modes close to the quantum ground state.

Findings

Achieved phonon occupation of less than 10 at 5 K.

Identified thermal noise in cavity elements as a limiting factor.

Discussed methods to mitigate thermal effects for ground state cooling.

Abstract

We describe a cryogenic cavity-optomechanical system that combines Si3N4 membranes with a mechanically-rigid Fabry-Perot cavity. The extremely high quality-factor frequency products of the membranes allow us to cool a MHz mechanical mode to a phonon occupation of less than 10, starting at a bath temperature of 5 kelvin. We show that even at cold temperatures thermally-occupied mechanical modes of the cavity elements can be a limitation, and we discuss methods to reduce these effects sufficiently to achieve ground state cooling. This promising new platform should have versatile uses for hybrid devices and searches for radiation pressure shot noise.