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Two-photon quantum well infrared photodetectors below 6 THz

Franke, C.; Walther, M.; Helm, M.; Schneider, H.


Two-photon quantum well infrared photodetectors (QWIPs) are nonlinear detectors for the mid-infrared and terahertz regimes optimized for resonant two-photon absorption. Here we present first results on two-photon QWIP samples based on the GaAs/AlGaAs material system with intersubband energies between 25 and 12 meV (6 to 3 THz) confirmed by photocurrent spectra. The dark current showed large discontinuities, presumably caused by impact ionization. We performed interferometric autocorrelation experiments at the free-electron laser FELBE and observed nonlinear interferograms for all samples.

Keywords: quantum well infrared photodetector; QWIP; interferometric autocorrelation; nonlinear optics; two-photon absorption

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