We review the principles of a new kind of optical Doppler frequency detectors and their applications to laser radars. These novel optical frequency sensors are based on the recently investigated moving space charge field effects found in photoconductive semiconductors. The photocurrent generated by the moving space charge field photodetectors is linearly proportional to the Doppler frequency shift suffered by the probing signal beam relative to the local reference laser beam and constitutes the unique directional discrimination capability in optical frequency detection not easily found in other forms of Doppler frequency detection schemes. Application of these novel Doppler frequency detectors to laser radars lead to significantly compact, economical, and power efficient systems. Simple feasibility demonstration of the proposed concept is also presented.
We report for the first time the growth of high quality Zn Te epilayers on silicon substrates by Metal Organic Vapor Phase Epitaxy (MOVPE). ZnTe layers up to 7μm thick were grown on (001) silicon substrates at 420°C-450°C substrate temperatures. The layers were mirror shiny and smooth, devoid of growth features like layered or stepped structures. The x-ray double crystal diffraction showed that best ZnTe layers exhibited Full Width at Half Maximum (FWHM) of 110 arc seconds. Further optimization of the growth procedure will make this material very useful for the potential development of iow cost infrared focal plane arrays and other optoelectronic devices which use direct wide band gap ZnTe.
InP acoustooptic Bragg cells which are IR-transparent in the 1-10 micron bandpass have a center frequency in the 200-600 MHz range, and a diffraction efficiency of 40-60 percent, on the basis of 1-W RF driving power. These devices are anticipated to be ideal in such applications as fiber-optic modulators, IR scanners, deflectors, and HF mode-lockers. In the course of fabrication, the photoelastic constant p44 has been defined; using other crystallographic configurations, such photoelastic constants as p11 and p12 are expected to emerge.
The Ge3As12Se55 glass is proven to be an excellent acousto—optic material for low power applications. High diffraction efficiency, low acoustic attenuation, low optical insertion loss, and isotropic properties make it an ideal candidate for signal processing and fiber—optic applications.
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