Uncooled VLWIR FPA Using Interferometry

"We propose to develop a very long wave infrared (VLWIR) FPA (focal plane array) for missile seeker and space surveillance applications, for which the LWIR region is very important. It consists of a 2-D array of micromachined micro Fabry-Perotinterferometers (FPIs), each of which contains a micro airgap cavity formed by two partially-reflecting mirrors, enclosing a micro-volume of air, and a photvoltaic detector sensitive to visible radiation. One of these mirrors is attached to a movablemembrane that forms one wall of the cavity. When VLWIR radiation falls on the cavity, the movable mirror moves relative to the non-movable mirror due to the heating of the air by the incident VLWIR. This movement causes an interference of the visible lightbeam allowed to incident the cavity, and the inteference amplitude proportional to the heating of the cavity is detected by the visble photovoltaic detector attached to the non-movable mirror. Thus, the photovoltaic detector is highly sensitive to theVLWIR radiation falling on the cavity. The proposed FPA is essentially an array of visible detectors operated at room temperature and fabricated with the 0.25-micron CMOS (complementary metal-oxide semiconductor) process. Its high VLWIR sensitivity is dueto the interference effect caused by heating of the micro-volume of air in the cavity. Its fabrication involves the CMOS as well as the MEMS (micro electro-optical mechanical system) process technologies. Phase 1 will define the FPA system requirements,design the FPA system structure and delineate the fabrication processes. Phase 2 will fabricate the FPA using foundries and integrate and test a beadboard FPA system. Missile tracking, weapon systems, medical imaging and gas sensing"