A cryogenic multiaxis range-resolved laser interferometer

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Christiansen, Adam J.
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy
Building upon the successes of previous far-infrared space astronomy missions that initially featured small but cold (<4 K) or large but warm telescopes, the future path is clear: the next generation of far-infrared telescopes must be both large and cold, which requires cryogenic cooling of the mirrors, instrumentation, and detectors. The precision to which the moving cryogenic components of the instrument must be measured and controlled demands a robust low power position metrology system, and a cryogenic multiaxis range-resolved laser interferometer using a sinusoidal frequency modulation (SFM) technique was investigated to solve this problem. The development included cryogenic considerations and characterization of several fibre and optical components, calibration of the selected hardware, and verification of the technique. Simultaneous multiaxis measurements were demonstrated at ambient and cryogenic temperatures of <6 K, and the measured performance under ambient conditions showed a resolution of ~50 pm and a stability of 0.4 nm rms in a 20 Hz bandwidth. The demonstrated performance exceeds that which is required by proposed far-infrared missions and distinguishes the SFM range-resolved laser interferometer as a leading candidate for future space-based applications.
Laser , Metrology , Range-resolved , Interferometry , Cryogenic , Optics , Photonics , Fiber , Fiber optics , Astronomy , Astrophysics , Multiaxis , Multiplexing , FPGA , Signal processing , DSP , Ranging , Displacement , Frequency modulation , Embedded systems , Far-infrared