We experimentally observed for the first time two-photon detection in a quantum dot mid-infrared photodetector. We use a 100-fs difference frequency generator tuned in the 2-5 micron range. The photodetector is suitable for second-order autocorrelation measurements for mid-infrared optical pulses. ©2002 Optical Society of America.
Photons;Light absorption;Semiconductor quantum dots;Infrared detectors;Laser pulses;Fourier transform infrared spectroscopy;Correlation methods;