A cryogenic multiaxis sinusoidal frequency modulation range-resolved laser interferometer for far-infrared space-based astronomical instrumentation

Citation

A. Christiansen, D. Naylor, and B. Gom. "A cryogenic multiaxis sinusoidal frequency modulation range-resolved laser interferometer for far-infrared space-based astronomical instrumentation". Measurement Science and Technology, 37(8):085003, 2026. DOI: 10.1088/1361-6501/ae411f.
Journal Article

Abstract

The next generation of far-infrared space observatories must be cryogenically cooled to fully exploit the sensitivity of state-of-the art detectors. It is widely accepted that a Fourier transform spectrometer (FTS) is the optimum solution for high-resolution spectroscopy. The FTS itself requires precision, low-power, and robust cryogenic displacement metrology; previous missions have used capacitive, inductive, and optical encoder displacement metrology systems, however, to date, no mission has flown a cryogenic range-resolved laser interferometer for such a purpose. Interferometers confer advantages of high precision and low thermal power dissipation that can meet the stringent requirements of future missions. We have developed a cryogenic, multiaxis, range-resolved laser interferometer based on sinusoidal frequency modulation (SFM) that requires only a single laser and a single photodetector to simultaneously measure up to eight axes. We present the theory, key design considerations, calibration methods, and application of the SFM technique to simultaneous multiaxis measurements under both ambient and cryogenic conditions. To the best of our knowledge, the latter represents, for the first time, simultaneous cryogenic multiaxis displacement measurements using a probing beam launched within the cryogenic workspace.