Silicon-nitride nanosensors toward room temperature quantum optomechanics

TL;DR

This paper explores silicon-nitride nanosensors for room temperature quantum optomechanics, focusing on optimizing mechanical quality factors and coupling parameters through theoretical and experimental analysis of edge loss mechanisms.

Contribution

It provides a comparative study of edge loss mechanisms in state-of-the-art silicon-nitride resonators, offering design guidelines for ultra-coherent quantum optomechanical devices.

Findings

Edge dissipation significantly affects $Q imes u$ in nanomembranes.

Clamp-tapering and soft-clamping reduce edge losses.

Experimental results align with theoretical models of loss mechanisms.

Abstract

Observation of quantum phenomena in cryogenic, optically cooled mechanical resonators has been recently achieved by a few experiments based on cavity optomechanics. A well-established experimental platform is based on a thin film stoichiometric ($ Si_3 N_4 $) nanomembrane embedded in a Fabry-Perot cavity, where the coupling with the light field is provided by the radiation pressure of the light impinging on the membrane surface. Two crucial parameters have to be optimized to ensure that these systems work at the quantum level: the cooperativity $ C$ describing the optomechanical coupling and the product $ Q \times \nu$ (quality factor - resonance frequency) related to the decoherence rate. A significant increase of the latter can be obtained with high aspect-ratio membrane resonators where uniform stress dilutes the mechanical dissipation. Furthermore, ultra-high $Q \times \nu$ can be reached by drastically reducing the edge dissipation via clamp-tapering and/or by soft-clamping, virtually a clamp-free resonator configuration. In this work, we investigate, theoretically and experimentally, the edge loss mechanisms comparing two state-of-the-art resonators built by standard micro/nanofabrication techniques. The corresponding results would provide meaningful guidelines for designing new ultra-coherent resonating devices.