Generation and detection of terahertzpulsed radiation with photoconductive antennas and its application toimaging

Abstract

We describe the basic properties of photoconductive (PC)antennas as emitters and detectors of terahertz (THz) pulsedradiation. The efficiency of PC antennas is discussed, taking intoaccount the saturation effect due to field screening byphoto-generated carriers. We show that maximum emission efficiencyunder a constant pump power condition is achieved by adjusting the PCgap size so that the pump intensity (power divided by PC area) isequal to the characteristic saturation intensity. We also discuss thebandwidth of PC antennas and conclude that PC antennas are capable ofgenerating and detecting ultra-broad THz radiation beyond 10 THz whenshort enough laser pulses are used. Our conclusion is demonstratedexperimentally by detecting ultra-broadband THz radiation, whosespectrum distributed up to 40 THz, with a PC antenna. As an exampleof applications of THz pulsed radiation based on a PCemitter-detector system, results for the imaging of objects inpowders are presented and discussed.