Multicolor infrared detection using a voltage tunable bandpass filter

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Abstract
It was demonstrated that an electron energy bandpass filter placed next to a quantum well infrared photodetector (QWIP) is not only able to suppress dark current, but also is able to select photocurrents of different energies. Since the bandpass energy of the filter changes with an applied bias across the filter, this mechanism can be used to control the detection width and the cutoff wavelength of the detector. If the photoresponse of the QWIP has more than one energy peak, the same filter can also be used to intercept a particular photoelectron peak and achieve voltage tunable multicolor infrared detection. In this work, we also show that the bandpass filter increases the background limited temperature and the detectivity of the QWIP by filtering away the lower energy dark current and the unused photocurrent.