Improved Acousto-Optic Modulators For CO[sub]2[/sub] Heterodyne Laser Systems

K. F. Hulme; J. T. Pinson

doi:10.1117/12.935905

13 December 1983 Improved Acousto-Optic Modulators For CO₂ Heterodyne Laser Systems

K. F. Hulme, J. T. Pinson

Proceedings Volume 0415, Coherent Infrared Radar Systems and Applications II; (1983) https://doi.org/10.1117/12.935905
Event: 1983 Technical Symposium East, 1983, Arlington, United States

Abstract

The features of the RSRE chirp-modulated CW CO2 laser rangefinder/velocimeter based on a purpose-built acousto-optic modulator are briefly restated. The significance of acoustic reflections inside the acousto-optic modulator is described, particularly their increased importance when the transition to a single transmit/receive aperture is attempted; the need then arises to provide effective 60 MHz acoustic damping in the modulator block. Experiments with tungsten-loaded epoxy, with chill-cast Wood's metal layers and with electroplated indium layers are described. Acoustic damping effects are assessed quantitatively on acoustical and optical test benches. It is found that indium layers provide practical effective damping and open the way for single-aperture heterodyne CO2 systems of the modulated-CW type. Optical measurements on modulator blocks shaped to reduce acoustic reflections show that indium damping reduces the first unwanted modulated pulse emerging from the modulator due to acoustic reflections down to -55 db in power relative to the initial wanted pulse, compared with -38 db for uncoated block; unwanted pulses emerging later are reduced even more powerfully and long-delayed pulses become unobservably small.

Citation Download Citation

K. F. Hulme and J. T. Pinson "Improved Acousto-Optic Modulators For CO₂ Heterodyne Laser Systems", Proc. SPIE 0415, Coherent Infrared Radar Systems and Applications II, (13 December 1983); https://doi.org/10.1117/12.935905

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