Dithered-edge sampling of terahertz pulses

We introduce a technique for ultrawideband measurement of terahertz pulses called dithered-edge sampling ~DES!. The technique makes use of a photoconductive receiver, but the detection bandwidth is much wider than that of the receiver alone. The key to increasing the bandwidth is the addition of an ultrafast optically triggered attenuator that chops the terahertz pulse before its detection. The bandwidth is limited only by the duration of the optical pulse used to trigger the attenuator. We use a combination of derivative dither and an integrating receiver to recover the terahertz field directly from the measured signal. When used alone, the slow receiver blurs the measured terahertz pulse width to 1.3 ps. However, the increased time resolution of the DES system ~triggered attenuator plus receiver! allows one to measure source-limited terahertz pulse widths ~400 fs in this case!. © 1999 American Institute of Physics. @S0003-6951~99!04541-6#