Sail Membranes Enable Low-Frequency Optomechanical Accelerometers

Bayesian-optimized silicon nitride “sail” membranes cut resonant frequency by about 10× while preserving Q–mass product, enabling a kHz optomechanical accelerometer with 40 ng₀/√Hz thermal noise.

TL;DR — Bayesian-optimized Si3N4 sail membranes lower resonant frequency by about 10× while preserving Q×mass. The authors report centimeter-scale kHz devices with Q ~10^7 and Q×mass ~10 g, plus a monolithic 7 kHz optomechanical accelerometer with 40 ng₀/√Hz room-temperature thermal noise.

Background: measuring motion with light and membranes

Accelerometers measure acceleration from vibration, gravity, and other forces. Consumer versions sit in phones and cars; precision versions aim to detect much smaller motion, down to tiny fractions of Earth’s gravitational acceleration.

Optomechanical accelerometers use a mechanical resonator as the inertial element and light to read out its motion. Their sensitivity depends on both the mechanical design and the optical measurement.

The paper focuses on strained silicon nitride (Si3N4) membranes: thin, tensioned structures that can achieve very low mechanical loss when carefully engineered.

Full analysis is available via x402 micropayment.