Novel optical Doppler frequency detector based on moving space charge field effects in semiconductors and its application to laser raders

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.