Ultrafast detection and autocorrelation of picosecond THz radiation pulses with a GaAs/AlAs superlattice

We used a wide miniband GaAs/AlAs superlattice (at room temperature) for detection and autocorrelation of picosecond THz radiation pulses (frequency 4.3 THz) from a free- electron laser. The detection was based on a THz-field induced change in conductivity of the superlattice, and the correlation on the nonlinearity of the conductivity change at strong THz-pulse- power. The nonlinear conductivity change was due to two effects, which we attribute to dynamical localization of miniband electrons and to ionization of deep impurity centers. (C) 1998 American Institute of Physics. [S0003-6951(98)04946-8].