Three photon-absorption autocorrelation in a GaAsP photodiode

Summary form only given. Most recently, two-photon-absorption (2PA) conductivity in semiconductors has become an attractive alternative to second-harmonic generation for the measurement of ultrashort pulses. The method is based on the generation and detection of a photocurrent proportional to the square of the intensity in a semiconductor whose bandgap exceeds the photon energy of the pulses. We report three-photon-absorption (3PA) conductivity in a GaAsP photodiode and its use to achieve optical autocorrelation of short pulses. The /spl sim/150 fs pulses are generated by an optical parametric oscillator tunable from 1.4 to 1.6 /spl mu/m. A standard Michelson-type setup with a speaker allows for real-time autocorrelation. The delayed optical pulses are focussed to a spot size of /spl sim/4 /spl mu/m on the photodiode.