Microlenses on Focal-Plane Arrays of QWIPs

The performances of large focal-plane arrays of quantum-well infrared photodetectors (QWIPs) would be improved, according to a proposal, by incorporating microlenses. In comparison with a similar QWIP array that lacked microlenses, a QWIP array with microlenses could be made to exhibit less dark current [and thus a greater signal-to-noise ratio (SNR)] at a given temperature. Alternatively, the QWIP array with microlenses could be made to exhibit a given SNR at a higher temperature; this would be advantageous in that it would open up the possibility of operating QWIPs in infrared cameras at higher temperatures, reducing the cost of cooling the QWIPs to obtain adequate SNRs.