Chen-Chia Wang

Applications of Novel Coherent Optical Sensors Based on Moving Space Charge Field Effects in Photoconductive Semiconductor Devices

The interference between two laser beams forms an optical intensity interference pattern inside photoconductive semiconductor devices. The spatially non-uniform optical intensity distribution causes the diffusion of photo-generated free charge carriers and results in the formation of an internal space charge electric field in the equilibrium. When the center frequencies of the laser beams are not equal, the internal space charge field is set in motion and drifts free charge carriers out of the semiconductor devices, resulting in measurable photocurrents which contain information regarding the relative magnitudes of the laser oscillating frequencies. This talk presents a brief introduction of the moving space charge field effects in various semiconductor devices/structures and their applications in the fields of laser Doppler velocimetry, vibrometry, and spectroscopy.