A two-photon detector based on intersubband transitions in GaAs/AlGaAs quantum wells operating in the Terahertz regime below the Reststrahlenband is reported. Resonantly enhanced optical nonlinearities enables sensitive quadratic detection at pJ pulse energies. We demonstrate its use in a quadratic autocorrelator for far-infrared picosecond pulses at around 7 THz.
Forschungszentrum Dresden Rossendorf, Institute of Ion Beam Physics and Materials Research, P O Box 510119, D-01314 Dresden, Germany. h.schneider@fzd.de
