Spectrally adaptive infrared photodetectors with bias-tunable quantum dots

Quantum-dot infrared photodetectors (QDIPs) exhibit a bias-dependent shift in their spectral response. In this paper, a novel signal-processing technique is developed that exploits this bias-dependent spectral diversity to synthesize measurements that are tuned to a wide range of user-specified spectra. The technique is based on two steps: The desired spectral response is first optimally approximated by a weighted superposition of a family of bias-controlled spectra of the QDIP, corresponding to a preselected set of biases. Second, multiple measurements are taken of the object to be probed, one for each of the prescribed biases, which are subsequently combined linearly with the same weights. The technique is demonstrated to produce a unimodal response that has a tunable FWHM (down to Deltalambda similar to 0.5 mum) for each center wavelength in the range 3-8 mum, which is an improvement by a factor of 4 over the spectral resolution of the raw QDIP. (C) 2004 Optical Society of America.