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Optical Grating Enhancement of MWIR Structures for High Temperature Operation

Description:

TECHNOLOGY AREA(S): Sensors 

OBJECTIVE: Design and fabricate a resonant cavity midwave infrared (MWIR) detector for a proof of concept that utilizes a patterned metal layer (grating) to selectively enhance the optical absorption of the underlying device. The resulting detector should demonstrate a high quantum efficiency and higher operating temperature than a comparable state-of-the-art device without the grating, thus reducing the size, weight, and power (SWaP) requirements for long range high resolution midwave infrared (IR) imaging sensors. 

DESCRIPTION: Advances in infrared detector technology remain limited by SWaP due to the need for cooling in dewar assemblies for peak performance. In order to provide the benefits of high-performance mid-wave IR imaging to small UAS and infantry weapon systems, sensor cooling requirements must be reduced so that detectors can be incorporated into lightweight sensor packages to enable enhanced awareness and long range object of interest identification in all battlefield conditions. Patterned resonator structures are a well-known concept for creating local enhancements to field intensities in optical structures (see references and related literature). However, current III-V semiconductor technology (bulk and strained layer superlattice) have not yet achieved operation close to room temperature. By combining the latest in device materials and architecture (e.g. unipolar barrier devices) with a novel metal grating on the detector structure that uses optical resonance to greatly enhance the infrared absorption, the total absorber volume required can be reduced, enhancing the signal-to-noise ratio to allow for operation at higher temperatures accessible to thermoelectric cooling or even passive cooling. The overlaying grating pattern must be carefully designed to provide the maximum enhancement at a targeted wavelength for a specific device geometry. If successful, the high-temperature MW detectors enabled by this project will directly benefit the compact imaging sensors supporting the Solider Lethality, Next Generation Combat Vehicle, and Future Vertical Lift Army modernization priorities. 

PHASE I: Design a grating pattern for an antimonide-based MWIR detector using electromagnetic (EM) modeling that results in near-total absorption while also minimizing the required absorber layer thickness of the device. Demonstrate enhanced absorption in a fabricated test structure and accuracy of the EM model. Show that the model and device fabrication can be adjusted for a desired cutoff wavelength. 

PHASE II: Develop a working focal plane array and incorporate in a prototype device, including a readout integrated circuit and conduct testing in a realistic environment. 

PHASE III: The system could be used in a variety of applications where size and portability are paramount. This includes head mounted display systems, which could incorporate infrared sensors to enhance visibility in poor environmental conditions, highlight Identification Friend or Foe (IFF) signals, and to provide advanced warning of hostile activity. Commercial: high-performance MWIR cameras can be applied in commercial vehicle technology, both manned and autonomous. Room temperature MWIR detection can also be packaged in fused video surveillance and home security. 

REFERENCES: 

1: D. Z. Ting, A. Soibel, A. Khoshakhlagh, S. A. Keo, S. B. Rafol, A. M. Fisher, B. J. Pepper, E. M. Luong, C. J. Hill, S. D. Gunapala, Antimonide e-SWIR, MWIR, and LWIR barrier infrared detector and focal plane array development, Proc. SPIE 10624, Infrared Technology and Applications XLIV, 1062410 (2018)

2:  K. K. Choi, M. D. Jhabvala, J. Sun, C. A. Jhabvala, A. Waczynski, K. Olver, Resonator-quantum well infrared photodetectors, Appl. Phys. Lett. 103 (2013)

3:  C. Min, J. Li, G. Veronis, J.-Y. Lee, S. Fan, P. Peumans, Enhancement of optical absorption in thin-film organic solar cells through the excitation of plasmonic modes in metallic gratings, Appl. Phys. Lett. 96 (2010)

KEYWORDS: Sensors, Infrared, Midwave, Optical Grating, Focal Plane Array, Plasmonics 

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