Superlattice detector as a fast direct detector and autocorrelator for terahertz radiation

We report on a GaAs/AlAs superlattice detector as a novel direct detector and autocorrelator for THz radiation. It is based on a doped wide-miniband GaAs/AlAs superlattice, with submonolayer AlAs barrier layers; the superlattice is operated at room temperature. THz radiation, generated by a free-electron laser and a mode locked p-Ge laser, was coupled into the superlattice via a corner cube antenna system. THz-irradiation of the biased superlattice resulted in a current reduction, which was monitored. The direct detector showed a fast response (20 ps, limited by the electronic circuit) and was robust against intense radiation pulses (peak power 10 kW). The responsivity was 100 times higher than the responsivity of detectors of comparable risetime and comparable robustness. Intense THz radiation caused a complete suppression of the current through the superlattice. This is the basis of the superlattice autocorrelator. The superlattice autocorrelator could resolve picosecond radiation pulses.