INFRARED SLS FPAS ON DIGITAL-PIXEL ROICS FOR GREATLY IMPROVED SIGNAL-TO-NOISE PERFORMANCE

A measure of the signal-to-noise ratio of a focal plane array (FPA) is the temporal noise equivalent difference in temperature (NEDT) which is a function of FPA operating temperature, spectral band, photon flux, pixel size, and the charge-well-depth of the readout integrated circuit (ROIC). For ANALOG ROICs with typical 10-20 million electron (me-) well-depths, NEDT values of 20-30 mK are observed for longwave infrared type-II strained layer superlattice (LWIR SLS) FPAs. A recent development in the industry is the DIGITAL-PIXEL ROIC (DROIC) which uses a digital counter in each unit cell to greatly increase well-depth to 100 me- and higher. Since background-limited NEDT varies inversely as the square root of the well-depth, DROICs promise much lower NEDT of ~ 3 mK, which translates to detection of fainter objects, longer detection range, etc. In Phase I, we will fabricate and test both analog and digital FPAs (on analog and digital ROICs, respectively) from the same detector lot and compare performance. Sample FPAs will be delivered. In Phase II, we will develop and deliver a camera using the new DROIC. At a minimum, these new DFPAs will allow NASA to detect fainter infrared targets on the ground and in the sky.