Experimental Investigation of Terahertz Temporal Response of a Photoconductive Switch

Picosecond or subpicosecond electrical pulses can be generated from femtosecond laser excited photoconductive switches, and this technique is an effective method to characterize the rise time of the broadband oscilloscopes recently. In this paper, low temperature grown GaAs (LT-GaAs) is used as the substrate of the photoconductive switch which is excited by the femtosecond laser. After propagating along a coplanar waveguide, the generated terahertz pulses are transferred to a 1.85 mm coaxial cable through a microwave probe. The pulse width is measured in a 70 GHz sampling oscilloscope, the FWHM value is about 7.4 ps.