POLARIZATION-DEPENDENT EFFICIENCY OF PHOTOCONDUCTING THZ TRANSMITTERSAND RECEIVERS

The emission and detection efficiencies of photoconducting THz transmi tters and receivers are found to be sensitive to the polarization of t he optical gating pulse. Signal amplitudes from GaAs coplanar striplin e transmitters and silicon-on-sapphire dipole receivers vary by factor s of up to 4 and 3, respectively, with rotation of the exciting pulse polarization. In both cases, maximum signal is obtained when the polar ization of the normally incident light is perpendicular to the edge of the metal electrodes. This polarization sensitivity, which appears to arise from differences in the spatial distribution of photoexcited ca rriers in the semiconductor, needs to be considered when optimizing th e signal-to-noise ratio in coherent THz spectroscopy. (C) 1998 America n Institute of Physics.