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2004
Journal Article
Titel
Resonant two-photon photoemission in quantum-well infrared photodetectors
Alternative
Resonante Zwei-Photon-Photoemission in Quantentopf-Infrarot-Photodetektoren
Abstract
We report the nonlinear behavior of quantum-well infrared photodetectors with three energetically equidistant energy levels. The giant resonant nonlinearity leads to a quadratic power dependence of the photocurrent down to excitation power densities as low as 0.1 W/cm2. Using these highly sensitive two-photon detectors, second-order autocorrelation measurements of ultrashort midinfrared laser pulses in the pJ regime are demonstrated. The dynamical behaviour is studied by a numerical analysis of these measurements. At high bias voltages we observe a dominating linear contribution to the photocurrent arising from tunnelling processes.