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Resonant two-photon photoemission in quantum-well infrared photodetectors

Resonante Zwei-Photon-Photoemission in Quantentopf-Infrarot-Photodetektoren
: Maier, T.; Schneider, H.; Walther, M.; Koidl, P.; Liu, H.C.


Applied Physics Letters 84 (2004), No.25, pp.5162-5164
ISSN: 0003-6951
ISSN: 1077-3118
Journal Article
Fraunhofer IAF ()
two photon absorption; Zwei-Photon-Absorption; quantum well; Quantentopf; QWIP; autocorrelation; Autokorrelation; resonant nonlinearity; resonante Nichtlinearität

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.