Multiple- and single-shot autocorrelator based on two-photon conductivity in semiconductors

Two-photon-induced conductivity has been observed in Si and GaAsP photodiodes and in a CdS photo-conductive cell at room temperature and applied to the ultrashort optical pulse measurement with a simplified Michelson-type arrangement. The efficiency of the two-photon conductivity is found to be 3 x 10(-14)I A/W, where I is the intensity of the incident pulse in watts per squared centimeter. A single-shot pulse-width measurement has also been performed by using a two-dimensional silicon CCD array. Use of these inexpensive photodetectors with nonlinear characteristics has proved to be convenient for intensity correlators because of their instantaneous response to temporal coincidence of optical pulses and ease of optical arrangement.