Dynamic aperture optical arrays based on polymeric MEMS actuators for large scale coding elements with application in visible to MWIR


Extension of coded apertures to the MWIR introduces the effects of diffraction and other distortions not observed in shorter wavelength systems. A new approach is being developed under the DARPA/SPO funded LACOSTE (Large Area Coverage Optical search-while Track and Engage) program, that addresses the effects of diffraction while gaining the benefits of coded apertures, thus providing flexibility to vary resolution, possess sufficient light gathering power, and achieve a wide field of view (WFOV). The photonic MEMS "eyelid" array technology is currently being instantiated in this DARPA Surveillance program study as the "heart", mediating the flow of the incoming signal. However, speed, lifetime, packaging and scalability are critical factors for the MEMS "eyelid" technology which will determine system efficacy as well as military and commercial usefulness. The electronic eyelid array is the fundamental addressable unit for adaptive code generation and will allow the system to multiplex in time for increased resolution. The binary code which determines whether a 500μm eyelid is open or closed is referred to as the "eyelid code." Groups of eyelids can work together as a "super aperture" by virtue of a "macro-code." A macro code becomes relevant to describe how dispersed eyelids across the 0.19m × 0.19m aperture will function together. Dynamic aperture arrays were fabricated on both quartz and sapphire substrates for operation in the visible to MWIR. Both 8×8 and 40×40 element arrays were designed, fabricated, and tested with macro-codes consisting of 4, 8, and 16 unique combinations. The die were packaged and tested in ambient for robust eyelid operations. The point spread function was also measured in an optical setup with the eyelid arrays located in the aperture plane.