2×10-13 Fractional Laser-Frequency Stability with a 7-cm Unequal-Arm Mach-Zehnder Interferometer

To achieve subpicometer sensitivities in the millihertz band, laser interferometric inertial sensors rely on some form of reduction of the laser-frequency noise, typically by locking the laser to a stable frequency reference, such as the narrow-line-width resonance of an ultrastable optical cavity or an atomic or molecular transition. In this paper, we report on a compact laser-frequency stabilization technique based on an unequal-arm Mach-Zehnder interferometer that is subnanometer stable at 10μHz, subpicometer at 0.5 mHz, and reaches a noise floor of 7fm/Hz at 1 Hz. The interferometer is used in conjunction with a dc servo to stabilize the frequency of a laser down to a fractional instability below 4×10-13 at averaging times from 0.1 to 100 s. The technique offers a wide operating range, does not rely on complex lock-acquisition procedures, and can be readily integrated as part of the optical bench in future gravity missions. © 2023 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society.