Article No. spmi.1998.0614 Available online at http://www.idealibrary.com on Superlattices and Microstructures, Vol. 25, No. 1/2, 1999 A GaAs/AlAs superlattice autocorrelator for picosecond THz radiation pulses S. WINNERL, S. P ESAHL, E. S CHOMBURG, J. GRENZER, K. F. RENK Institut f ¨ ur Angewandte Physik, Universit¨ at Regensburg, Germany H. P. M. P ELLEMANS , A. F. G. VAN DER MEER FOM-Institute for Plasma Physics ‘Rijnhuizen’, Nieuwegein, The Netherlands D.G. PAVEL’ EV ,YU.KOSCHURINOV , A. A. I GNATOV Department of Radiophysics, Nizhny Novgorod State University, Russia B. MELZER, V. USTINOV , S. I VANOV , P. S. KOP ’ EV A.F. Ioffe Physico-Technical Institute, Politechnicheskaya 26, 194021, St Petersburg, Russia (Received 26 October 1998) We report on a GaAs/AlAs, wide-miniband, superlattice autocorrelator for picosecond THz radiation pulses (operated at room temperature); the autocorrelator is based on the THz radiation-induced reduction of current through the superlattice. THz radiation (frequency 7.2 THz) from the FELIX (free-electron laser for infrared experiments) was coupled into the superlattice with an antenna system. We measured the current reduction for two time- delayed pulses and found that the signal decreased when the time delay was smaller than the pulse duration. With this superlattice autocorrelator we were able to resolve laser pulses that had a duration of a few picoseconds. c  1999 Academic Press Key words: autocorrelator, THz radiation, miniband transport, dynamical localization. 1. Introduction It has been found that THz fields (frequency 3.3 THz) interact with the miniband electrons in a wide- miniband superlattice and cause a reduction of current through the superlattice [1]. Recently it has been shown that strong THz fields (3.9 THz) can lead to a full suppression of current [2]. In this paper we report on a correlation experiment with THz radiation at a much higher frequency (7.2 THz), which is based on the saturation of current reduction for intense THz fields. 2. Experimental We irradiated a current-carrying superlattice (inset of Fig. 1A; U , static voltage; I , direct current) with two time-delayed laser pulses. The THz field induced a current change δ I which depended on the time delay. 0749–6036/99/010057 + 04 $30.00/0 c  1999 Academic Press