Measurement of electrical signals with picosecond resolution

Abstract

Electrical signals are measured (analyzed and displayed) with picosecond resolution by the electrooptic sampling of the signal being analyzed in a traveling wave Pockels cell. Sampling pulses, from an optical pulse generator such as a colliding pulse mode-locked laser, of subpicosecond duration are transmitted through the cell as polarized light and translated into a difference output corresponding to the difference in amplitude between the transmitted and rejected components of the polarized light. The signals, synchronous with the optical sampling pulses, are generated to propagate along the cell in a direction transverse to the transmission of the optical sampling pulses and in variably delayed relationship therewith. A separate beam of the optical pulses is desirably chopped and used to activate a photoconductive device which produces the signals. The difference output is processed, preferably by a lock-in amplifier and signal averager; the lock-in amplifier being synchronized with the chopping of the launched pulses, and displayed on a time base synchronous with the variable delay of the pulses. Accordingly, the signal is displayed on an expanded time scale for measurement and other analysis. The response of photodetectors, photoconductive switches and other ultrafast light activated devices can be determined, when these devices are used as the source of the signals being analyzed and displayed.