Ultrafast photon drag detector for intersubband spectroscopy

The Photon drag effect of a 2D electron gas is measuring the ps infrared pulses of the wavelength-tunable free electron laser source FELIX. The pulsed photon drag rseponse is found to depend critically on the coupling characteristics of the electrical circuit. We therefore developed an impedance and velocity matced photon drag detector. It consist of a GaAs/ AlGaAs multi quantum well sample which forms an integral part of a microstrip line. A Ge-prism enable incoupling at the critical 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 the intersubband resonance is investigated at room temperature at T=100 K. An analysis of the spectral lineshape of the Photon drag current response yields information about the momentum relaxation times of the electron in the ground and excited subbands.