26 April 1995 Laser diode edge sensors for adaptive optics segmented arrays: part 2-laser diode coupled integrated optics chip
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Abstract
Adaptive optics (AO) segmented array systems require los cost nm (piston) and (mu) rad (tilt) range displacement edge sensors to assist in establishing phase continuity between adjacent segments by measuring relative AO edge displacements. Preliminary laboratory experiments using Si based integrated optic (IO) chips coupled to laser diode sources were carried out to determine their suitability as low cost, miniature, reliable and high precision piston and tilt edge sensors. Edge sensor displacement experiments demonstrate a resolution (sensitivity) on the order of 10 nm. The IO chip used is a micro-version (7.5 X 7.5 X 0.5 mm3) of a double beam Michelson interferometer with a phase shifter to allow direction determination. Operating at a wavelength 770 < (lambda) < 790 nm and a power output < 50 (mu) W, the wavelength stability, within a temperature range 15 to 35 degree(s)C, is (Delta) (lambda) 0/(lambda) 0 equals 10-6. A 1 kHz frequency response was achieved for displacements on the order of 100 micrometers (measuring range) and 106 Hz at 100 nm displacement, with a logarithmic frequency response increasing with decreasing measuring range. The maximum linear (moving) relative speed between adjacent segments is 200 mm/s or 200 X 106 nm/s, allowing MHz sampling rates. Synchronously calibrated experiments of IO performance against a capacitance gauge, closed loop calibrated piezo stepper, and a HeNe source interferometer are presented. Systems integration design of the IO chip as a sensor is described.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
John L. Remo, John L. Remo, "Laser diode edge sensors for adaptive optics segmented arrays: part 2-laser diode coupled integrated optics chip", Proc. SPIE 2376, Laser Power Beaming II, (26 April 1995); doi: 10.1117/12.208204; https://doi.org/10.1117/12.208204
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