ULTRAFAST PHOTON DRAG DETECTOR FOR INTERSUBBAND SPECTROSCOPY

The photon drag effect of a 2D electron gas is measured using the ps i nfrared pulses of the wavelength-tunable free electron laser source FE LIX. The pulsed photon drag response is found to depend critically on the coupling characteristics of the electrical circuit. We therefore d eveloped an impedance and velocity matched photon drag detector. It co nsists of a GaAs/AlGaAs multi quantum well sample which forms an integ ral part of a microstrip line. A Ge-prism enables incoupling at the cr itical total reflection angle. This novel transmission line integrated photon drag detector (TIP-detector) generates signal transients below 10 ps rise and fall times. Its continuous spectral response through t he intersubband resonance is investigated at room temperature and at T =100 K. An analysis of the spectral lineshape of the photon drag curre nt response yields information about the momentum relaxation times of the electrons in the ground and excited subbands. (C) 1996 Academic Pr ess Limited