Infrared focal plane array based on MWIR/LWIR dual-band QWIPs: Detector optimization and array properties

Quantum well infrared photodetectors (QWIPs) have gained maturity for large focal plane arrays (FPA) with excellent thermal resolution, low 1/f noise, low fixed-pattern noise, and high pixel operability. Due to their spectrally narrow absorption, QWIPs are particularly suitable for thermal imaging applications involving several atmospheric transmission bands or several colors within the same band. We report on our progress on dual-band QWIP FPAs with pixel-registered, simultaneous integration in both bands. The arrays with 384 x 288 pixels and 40 mu m pitch are based on a photoconductive QWIP for the 3 - 5 mu m regime (MWIR) and a photovoltaic “low-noise” QWIP for 8 - 12 mu m (LWIR). Excellent noise-equivalent temperature differences of only 20.6 mK (LWIR) and 26.7 mK (MWIR) have been achieved at 6.8 ms integration time and f/2 aperture. In addition, we have investigated test devices with different gratings, and discuss their dual-band coupling efficiencies