InGaAs-on-Si photodetectors for high-sensitivity detection

Programs in both the U.S. and Britain are attempting to apply staring array technology to the ship-board infrared search and track (SBIRST) problem. A prime objective is to speed processing time, the previous generation of 360 deg scanners having a refresh rate of only 0.5-1.0 Hz. Another objective is to enhance sensitivity using much longer integration times. An impediment, though, is that if all pixels of resolution angle ∅ were to be viewed simultaneously with dedicated detectors each of width w, the total net length of detector material would then have to be very large: 2πw/∅ = 1.57 m = 60" for 100 μRad resolution and 25 μm detectors. So the application of staring array technology to horizon surveillance needs some form of wide viewing technique involving a combination of asymmetric resolution, reduced resolution, split optics or LOS stepping. The present paper suggests that conventional NEI is not the preferred unit of measure for guiding design choices but that instead a form of BLIP S/N can be both simple and intuitive. This S/N unit of measure is used to compare the two main choices for how to adapt staring technology to the horizon surveillance problem.