Two-photon photoconductivity in SiC photodiodes and its application to autocorrelation measurements of femtosecond optical pulses

By measuring the output signal of a SiC photodiode under short-pulse illumination with photon energies below the band gap, it was found that the response is determined by a second-order process, i.e., two-photon induced photoconductivity. This nonlinearity is suitable for realizing autocorrelation measurements of short laser pulses in the visible region (420-760 nm), where the nonlinear element and the photodetector are integrated in a single device. Laser pulses of 90-fs duration have successfully been measured with this technique.