The network of interferometric gravitational-wave observatories has successfully detected tens of astrophysical signals since 2015. In this paper, we experimentally investigate compact sensors that have the potential to improve the sensitivity of gravitational-wave detectors to intermediate-mass black holes. We use only commercial components, such as sensing heads and lasers, to assemble the setup and demonstrate its subpicometer precision. The setup consists of a pair of Michelson interferferometers that use deep frequency modulation techniques to obtain a linear, relative displacement readout over multiple interference fringes. We implement a laser-frequency stabilisation scheme to achieve a sensitivity of 0.3\,pm/Hz above 0.1\,Hz. The device has also the potential to improve other experiments, such as torsion balances and commercial seismometers.
@article{arxiv.2202.10274,
title = {Compact Michelson interferometers with subpicometer sensitivity},
author = {Jiri Smetana and Rebecca Walters and Sophie Bauchinger and Amit Singh Ubhi and Sam Cooper and David Hoyland and Richard Abbott and Christoph Baune and Peter Fritchel and Oliver Gerberding and Semjon Köhnke and Haixing Miao and Sebastian Rode and Denis Martynov},
journal= {arXiv preprint arXiv:2202.10274},
year = {2022}
}