Temporal measurements of ultrashort far infrared electromagnetic pulses

摘要

Dithered-edge sampling (DES) enables ultra-wideband measurement of terahertz pulses (far infrared electromagnetic pulses) using photoconductive antennas. The terahertz pulse is sampled by first passing it through a triggered photoconductive attenuator whose fast attenuation edge (limited only by the duration of the optical gating pulse) is dithered in time. A slow photoconductive receiver then measures the component of the terahertz electric field that is modulated at the dither frequency. The current through the photoconductive element constituting the receiver passes through a locking amplifier which may be operated at dither frequency. When used alone, the receiver blurs the measured terahertz pulse width. However, the increased time resolution provided by DES enables measurement of source-limited terahertz pulse widths. In addition, DES may be used to make direct measurements of a photoconductive receiver's temporal response.