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Proceedings Paper

Improved Acousto-Optic Modulators For CO2 Heterodyne Laser Systems
Author(s): K. F. Hulme; J. T. Pinson
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Paper 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.

Paper Details

Date Published: 13 December 1983
PDF: 9 pages
Proc. SPIE 0415, Coherent Infrared Radar Systems and Applications II, (13 December 1983); doi: 10.1117/12.935905
Show Author Affiliations
K. F. Hulme, Royal Signals and Radar Establishment (England)
J. T. Pinson, Royal Signals and Radar Establishment (England)


Published in SPIE Proceedings Vol. 0415:
Coherent Infrared Radar Systems and Applications II
Robert C. Harney, Editor(s)

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