Ultralow-Noise SiN Trampoline Resonators for Sensing and Optomechanics

TL;DR

This paper presents the development of ultralow-noise, high-quality SiN trampoline resonators with exceptional force sensitivity and long ringdown times, suitable for advanced sensing and optomechanics applications.

Contribution

The authors demonstrate wafer-scale fabrication of high-Q SiN trampoline resonators with record force sensitivity and compatibility with high-finesse optical cavities, advancing optomechanics technology.

Findings

Force noise sensitivity of 16.2 aN/Hz^{1/2} at room temperature

Quality factors above 4×10^7 and ringdown times over five minutes

High-finesse cavity integration with finesse 40,000

Abstract

In force sensing, optomechanics, and quantum motion experiments, it is typically advantageous to create lightweight, compliant mechanical elements with the lowest possible force noise. Here we report wafer-scale batch fabrication and characterization of high-aspect-ratio, nanogram-scale Si$_3$N$_4$ "trampolines" having quality factors above $4 \times 10^7$ and ringdown times exceeding five minutes (1 mHz linewidth). We measure a thermally limited force noise sensitivity of 16.2$\pm$0.8 aN/Hz$^{1/2}$ at room temperature, with a spring constant ($\sim$1 N/m) 2-5 orders of magnitude larger than those of competing technologies. We also characterize the suitability of these devices for high-finesse cavity readout and optomechanics applications, finding no evidence of surface or bulk optical losses from the processed nitride in a cavity achieving finesse 40,000. These parameters provide access to a single-photon cooperativity $C_0 \sim 8$ in the resolved-sideband limit, wherein a variety of outstanding optomechanics goals become feasible.