A novel laser frequency stabilization technique for FMCW systems

Citation

A. Christiansen, D. Naylor^*, M. Buchan, and B. Gom. "A novel laser frequency stabilization technique for FMCW systems". In: Photonic Instrumentation Engineering XII, 13373:133730C, 2025. San Francisco, USA. DOI: 10.1117/12.3040732.
Conference Proceedings Presentation

Abstract

There is a growing need for low power, precision metrology in spaced-based cryogenic environments. Displacement sensors used in previous space astronomy missions have included capacitive, inductive, and optical encoders, however, the need to reduce the power dissipation in the cryogenic workspace has driven a transition towards laser-based solutions. Our previous research has explored several range-resolved laser interferometry techniques suitable for cryogenic applications. Most recently, we have developed a frequency-modulated continuous-wave (FMCW) multi-axis laser interferometer based on the method of sinusoidal frequency modulation (SFM). This system has demonstrated, to the best of our knowledge, the first fully cryogenic (<4 K), simultaneous, multi-axis displacement measurements using a single laser and detector. While the SFM technique has not yet been implemented on a cryogenic space-based platform, it is the leading candidate for displacement metrology on the NASA PRIMA mission.

In the SFM technique, the optical frequency of the laser undergoes sinusoidal modulation about a central frequency. Any deviation of the central frequency from its assumed value introduces an error in the measured displacement. This paper introduces a novel concept for frequency stabilization of FMCW systems in which the central optical frequency is locked onto a molecular absorption line to provide a stability of 0.1 pm in wavelength. Preliminary results obtained using this calibration method in the context of SFM range-resolved laser interferometry are presented.