High resolution, wide field-of-view, infrared (IR) imagers find use in defense and civilian applications. The most demanding of them desire uniform sensitivity across an image’s field of view, while maintaining a small and light-weight optical design. These attributes can be achieved by curving of the focal plane array to reduce the need for field curvature correction. Using experimental and numerical methods, we investigated the spherical curving of hybridized arrays to demonstrate mechanical feasibility and opto-electronic performance. Each hybridized array comprised a 4k x 4k, 10 μm pixel pitch, midwave IR (MWIR) detector hybridized to a 67 mm diagonal fanout chip. We curve an array to 139.2 mm radius of curvature, resulting in a pixel area coverage of 0.086 sr. Measurements across the curved array revealed minimal variation in bandgap (<0.1 μm) and no appreciable difference in dark current.
High performance infrared focal plane arrays (FPAs) play a critical role in a wide range of imaging applications. However the high cost associated with the required cooling and serially processed die-level hybridization is major barrier that has thwarted Mid-wavelength Infrared (MWIR) detector technology from penetrating largevolume, low-cost markets. Under the Defense Advanced Research Projects Agency (DARPA) WIRED program, the HRL team has developed a wafer level integration schemes to fabricate large format Antimonidebased MWIR FPAs on Si Read Out Integrated Circuit (ROIC) as a means to achieve significant fab cost reduction and enhanced production scalability. The DARPA-hard challenge we are addressing is the thermal and stress management in the integration of two dissimilar materials to avoid detector and ROIC degradation and to maintain structure integrity at the wafer scale. In addition, a digital ROIC with extremely large well capacity was designed and taped-out, in order to increase the operating temperature of the FPAs. In this talk, we discuss our progress under the DARPA WIRED program.
This paper describes the design and demonstration of a 1024 element coded aperture subreflector array, implemented with single-bit phase shifters that utilize GaN HEMTs to modulate signals upon reflection. An active reflect-array enables digital beamforming using a single 235 GHz radar transceiver. Wafer level fabrication and assembly allows large arrays to be tiled up while maintaining reasonable costs.
Metamaterials are of substantial current interest because they may exhibit unusual and/or configurable optical responses. We studied the optical properties of gold and silver nanoparticles dispersed in different organic liquids in the visible to near-IR. Calculation of the refractive indices of metallic nanospheres or metallic-coated silica spheres in liquid crystals show the possibility of tuning and varying the refractive index by reorientation of the liquid crystal molecules. Measurements of the refractive indices of gold nanoparticles in dodecane were experimentally studied by using spectroscopic ellipsometry and a reasonable agreement with the theoretical results based on Mie scattering was obtained. Finally, the effect of gold and silver nanospheres on the nonlinear absorption properties of an organic liquid (L34, a 4,4'-dialkyl phenyleneethynylene) was studied. The results suggest that metallic nanoparticles dispersed in a host organic fluids can be good materials for fabrication of low and tunable index materials in the visible to near-IR wavelength range, and for the enhancement of the nonlinear absorption of liquids used in switching applications.
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