Ultralow-Noise SiN Trampoline Resonators for Sensing and Optomechanics

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.Comment: 8 pages, 4 figures, 1 tabl

Antibunching in an optomechanical oscillator

“…On the other hand, operation of a photonic crystal optomechanical cavity in the resolvedsideband regime has previously been reported in a different setup [6,48]. Thus, even though no single experimental setup currently satisfies all the requirements needed for realizing an antibunched phonon field, this may be remedied in the near-future due to recent advances in microfabrication and nanotechnology, which have led to an optical resonator with a quality factor of order 10 7 [49] and a mechanical oscillator with Q m = 10 8 [50]. In addition, the demonstration of a HanburyBrown-Twiss-type experiment [51] for a phonon field in a nanomechanical resonator paves the way to measuring the second-order correlation.…”

Spin detection with a micromechanical trampoline: towards magnetic resonance microscopy harnessing cavity optomechanics

“…In this article, we present work in which we harness a membrane resonator engineered for low mass and high-Q, known as a trampoline resonator [48][49][50] for spin detection [51][52][53]. Square SiN membranes have previously been used for MRFM [8], torque magnetometry [54], and force-detected ESR [55].…”

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