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Millimeter Wave Imaging with Metamaterials


OBJECTIVE: To develop a low-cost millimeter wave imager based on pyroelectric metamaterial absorbers. The goal is to develop an advanced composite detector fashioned from metamaterials that can be assembled into compact arrays for low cost hyperspectral and high sensitivity W-band imaging applications. DESCRIPTION: Millimeter wave imaging has been shown to be a useful tool in the detection of potential threats to military personnel. Examples include the use of millimeter wave imaging for chemical/biological detection, person-borne improvised explosive device detection, land-mine detection, and unmanned aerial system (UAS) detection. W-band (75 to 110 GHz) imagers have proven to be particularly useful to the military for the detection of threats. A low-cost solution to imaging in the millimeter wave region has the potential to provide significant benefits to numerous applications within the Department of Defense (DoD) Science & Technology programs. Electromagnetic metamaterials have demonstrated the ability to provide frequency dependent high absorptivity at millimeter wavelengths, and a W-band detector with optical read-out has been demonstrated. A common metamaterial absorber design uses a metal ground plane, dielectric layer, and a top layer of patterned metal. The metamaterial detectors use thin film pyroelectric materials as the dielectric spacer, thus enabling high absorptivity, and direct read-out of the detected signal. Metamaterial enhanced bimaterial cantilever pixels have been demonstrated for far-infrared detection. At least two types of metamaterial detector structures may be considered for millimeter wave imaging applications: (1) symmetric metamaterial absorbers (SMA) for coherent amplitude and phase detection, and (2) asymmetric or ground plane metamaterial absorbers (GPA), for intensity-only detection. While both SMA and GPA structures can be used for hyperspectral sensing, the coherent SMA structure provides phase sensitive, vector mode, sensing capabilities that are especially important in millimeter wave imaging applications. A W-Band imager should be able to detect objects at a distance of at least 10 meters and possess a noise equivalent temperature difference (NETD) of 5 degrees Kelvin (K) or less. The imager should be able to detect targets with a resolution of 10 cm or better at a distance of 10 meters. PHASE I: Develop and test a single pixel detector operating at 95 GHz. Demonstrate that the system can detect a NEDT of 5 degrees or less. Explore the use of a coherent structure that provides phase sensitive, vector mode, sensing capabilities. Develop a design of an imager operating in the W-Band that can detect objects to at least a distance of 10 meters with a resolution of 10 cm or better with a NEDT of 5 degrees K or less. PHASE II: Construct and demonstrate a working prototype W-Band imaging system using the design developed in Phase I. Demonstrate the imager using targets and black bodies at a distance of 10 meters or more. Demonstrate that the system can detect objects to at least a distance of 10 meters with a resolution of 10 cm or better with a NETD of 5 degrees K or less. Deliver the working prototype to the Government for further testing. PHASE III: Further research and development during Phase III efforts will be directed toward refining the final deployable equipment and procedures. Design modifications based on results from tests conducted using the Phase II deliverable will be incorporated into the system. Manufacturability specific to U.S. Army Concepts of Operation (CONOPS) and Chemical and Biological Defense Program end-user requirements will be examined. PHASE III DUAL USE APPLICATIONS: The development of a low-cost solution to imaging in the millimeter wave region has the potential to provide significant benefits to numerous programs within the DoD as well as other Government Agencies. REFERENCES: 1. P.K. Singh, K.A. Korolev, M.N. Afsar, S. Sonkusale, “Single and dual band 77/95/110 GHz metamaterial absorbers on flexible polyimide substrate,” Appl. Phys. Lett. 99, 264101 (2011). 2. H. Tao, E.A. Kadlec, A.C. Strikwerda, K. Fan, W.J. Padilla, R.D. Averitt, E.A. Shaner, X. Zhang, “Microwave and Terahertz wave sensing with metamaterials,” Opt. Exp. 19, 21620 (2011). 3. J.Y. Suen, K. Fan, J. Montoya, C. Bingham, V. Stenger, S. Sriram, W.J. Padilla, “Multifunctional metamaterial pyroelectric infrared detectors,” Optica 4, 276-279 (2017). 4. M.R. Webb, “A millimeterwave pyroelectric detector,” International Journal of Infrared and Millimeter Waves 12, 1225–1231 (1991). 5. T.W. Du Bosq, J.M. Lopez-Alonso, G.D. Boreman, D. Muh, J. 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Chen, H. Zhao, L. Yan, Y. Dai, “A new type of coherent electromagnetic radiation source based on interference effect between forward and backward waves in an active metamaterial slab,” Applied Physics A, (2019) 125:255. 11. Q. Yang, B. Li, Z. Lan, Y. Li, Z. Zhu, J. Shi, “Coherent absorption in optical metamaterials,” SPIE Proceedings, vol. 10824, Plasmonics III; 1082408 (2018). 12. H. Tao, W. J. Padilla, X. Zhang, and R. D. Averitt, “Recent progress in electromagnetic metamaterial devices for terahertz applications,” IEEE J. Sel. Top. Quantum Electron. 17(1), 92–101 (2011). KEY WORDS: millimeter wave imaging; metamaterials; hyperspectral; W-Band
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