Speaker
Description
Inertial sensors are essential tools for gravitational-wave detectors.
These detectors typically rely on Fabry-Pérot cavities that are actively stabilized to minimize mechanical noises in the frequency range of interest.
This stabilization demands precise monitoring of the mirrors motion using displacement sensors.
Various techniques have been developed for such inertial sensing, achieving impressive sensitivities using Fabry-Pérot cavities [1] or Michelson interferometers [2][3].
Heterodyne cavity tracking relies on measuring the beating between two optical cavities.
The stability of each cavity impacts the precision of this measurement since it involves a relative motion between the two cavities.
In this talk, we present proof of concept for a new method for heterodyne inertial sensing that enables absolute displacement measurement.
Using an optical frequency comb beating separately with two optical cavities, we can eliminate common-mode noise from the reference oscillator, effectively forming a balanced inertial sensor.
With this method, we reach a sensitivity of 700 fm/$\sqrt{\text{Hz}}$ at 1 Hz, close to the state-of-the-art of 260 fm/$\sqrt{\text{Hz}}$, and 10 fm/$\sqrt{\text{Hz}}$ at 1 kHz [1].
A projected two-orders of magnitude improvement in sensitivity will be discussed along with its potential applications in gravitational waves detectors.
[1] S. Chalathadka Subrahmanya, C. Darsow-Fromm, and O. Gerberding, Optics Express 33, 4044 (2025).
[2] M. B. Gray, D. E. McCLELLAND, M. Barton, and S. Kawamura, Optical and Quantum Electronics 31, 571–582 (1999)
[3] G. Zhao, B. Ding, J. Watchi, A. Deraemaeker, and C. Collette, Mechanical Systems and Signal Processing 145, 106959 (2020)