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This Defense Intelligence Reference Document, dated 2 March 2010, was prepared by the Defense Intelligence Agency's Defense Warning Office under the Advanced Aerospace Weapon System Applications program. It reviews invisibility through camouflage, transparency, and cloaking, covering metamaterials, transformation optics, and non-Euclidean broadband cloaking designs. It concludes that perfect cloaking is impossible, but imperfect devices could be made. Microwave cloaking is within reach of present technology, while visible-light invisibility remains uncertain and depends mainly on new theoretical research.
From the source:Release of 2026-09-18 Incident: 3/2/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD surveys the theory and early experiments behind invisibility cloaking, describing several ways an object might be hidden from visual or sensor detection, including camouflage, transparency effects, and optical cloaking that bends light around an object. It focuses mainly on metamaterials, negative refraction, and transformation optics, and reviews experiments that had already demonstrated limited cloaking at microwave frequencies. The report argues that “imperfect” cloaking is physically achievable in some parts of the electromagnetic spectrum, especially for microwaves, but that “perfect” cloaking is not practical because it would require material properties that conflict with the underlying physics. Its overall conclusion is that cloaking is a scientific field with plausible narrow applications, but that useful visible-light cloaking depends more on future theoretical breakthroughs than on conventional advances in materials science.
“The Advance”9 pages
UNCLASSIFIED/ /FOR OFFI@IAL l::ISE OHL¥ Summary A cloaking device is a passive device made of a transparent material that guides lig ht around any object in its interior as if the light has passed through empty space. The cloaking device conceals the object and hides the act of hid ing itself. Perfect cloaking devices are impossible because they require materials where t he speed of light approaches infinity. Imperfect cloaking devices could be made. Such devices implement suitable curved-space geometries. For electromagnetic microwaves, cloaking devices are definitely within reach of the present technology. Whether invisibility in t he visible range of t he spectrum will become a reality is not entirely clear yet. Most probably, this will depend more on the new t heoretical research than on advances in new materia ls, and on the application of mathematical intelligence, intuition, and imagination. 1 A. Alu and N. Engheta, Achieving transparency with plasmonic and metamateria l coatings, Physical Review E 72, 016623 (2005) . 2 G. W. Milton and N.-A . P. Nicorovici, On the cloaking effects associated with anomalous loca lized resonance, Proceed ings of the Royal Society London A 462, 3027 (2006). 3 Y. Lai, H. Chen, Z-Q. Zhang, and C. T. Cha n, Complementary Media Invisibility Cloa k that Cloaks Objects at a Distance Outside the Cloaking Shell, Physical Review Le tters 102, 093901 (2009) . 4 U. Leo nhardt, Optical Conformal Mapping, Science 312, 1777 (2006). 5 J. B. Pendry, D. Schurig, and D. R. Smith, Controlling Electromagnetic Fields, Science 312, 1780 (2006) . 6 J. B. Pendry, D. Schurig, and D. R. Smith, Controlling Electromagnetic Fields, Science 312, 1780 (2006) . 7 U. Leonhardt and T. G. Phi lbin, Transformation Optics and the Geometry of Light, preprint arXiv:0805.4778, to appear in Progress in Optics. 8 U. Leonhardt and T. G. Philbin, Transformation Optics and the Geometry of Light, preprint arXiv :0805.4778, to appear in Progress in Optics. 9 U. Leonhardt, Optical Conformal Mapping, Science 312, 1777 (2006) . 10 J. B. Pendry , D. Schurig , and D. R. Smith , Controlling Electromagnetic Fields, Science 312 , 1780 (2006) . 11 D. Schurig, J. J. Mock, B. J. Justice, S. A. Cummer, J. B. Pendry, A. F. Starr, and D. R. Smith, Metamaterial Electromagnetic Cloak at Microwave Frequencies, Science 314, 977 (2006) . 12 U. Leonhardt, Optical Conforma l Mapping, Science 312, 1777 (2006) . 13 D. Schurig, J. J. Mock, B. J. Justice, S. A. Cummer, J. B. Pendry , A. F. Starr, and D. R. Smith, Metamaterial Electromagnetic Cloak at Microwave Frequencies, Science 314, 977 (2006). 14 D. Schurig , J. J. Mock, B. J. Justice, S. A. Cummer, J. B. Pendry , A. F. Sta rr, and D. R. Smith, Metamaterial Electromagnetic Cloak at Microwave Frequencies, Science 314, 977 (2006) . 15 D. Schurig, J. J. Mock, B. J. Justice, S. A. Cummer, J. B. Pendry, A. F. Starr, and D. R. Smith, Metamaterial Electromagnetic Cloak at Microwave Frequencies, Scie nce 314, 977 (2006). 16 D. Schurig, J. J. Mock, B. J. Justice, S. A. Cummer, J.B. Pendry, A. F. Starr, and D. R. Smith, Metamaterial Electromagnetic Cloak at Microwave Frequencies, Science 314 , 977 (2006). 17 F. E. Wagner, S. Haslbeck, L. Stievano, S. Ca logero, Q. A. Pan khurst, and P. Martinek, Before striking gold in gold - ruby glass, Nature 407, 691 (2000). 18 D. Schurig, J. J. Mock, B. J. Justice, S. A. Cummer, J.B. Pendry, A. F. Starr, and D.R. Smith, Metamaterial Electromagnetic Cloak at Microwave Frequencies, Scie nce 314, 977 (2006). 19 W. Cai, U. K. Chettia r, A. V. Kildishev, and V. M. Shalaev, Optical cloaking with metamaterials, Nature Photonics 1, 224 (2007) . 20 W. Cai , U. K. Chettiar, A. V. Kildishev, and V. M. Shalaev, Optical cloaking with metamaterials, Nature Photonics 1, 224 (2007) . 21 C. M. Soukoulis, S. Linden, and M. Wegener, Costas M. Soukou lis, Stefan Linden, and Martin Wegener, Negative Refractive Index at Optical Wavelengths, Science 315 , 47 (2007) . 22 C. M. Soukoulis, S. Linden, and M. Wegener, Costas M. Soukoulis, Stefan Linden, and Martin Wegener, Negative Refractive Index at Optical Wavelengths, Science 315, 47 (2007) . 23 J. Yao, Z. Liu, Y. Liu, Y. Wang, C. Sun, G. Barta!, A. M. Stacy, and X. Zhang, Optical Negative Refraction in Bul k Metamaterials of Nanowires, Science 321 , 930 (2008). 24 J. Valentine, S. Zhang, T. Zentgraf, E. Ulin-Avila, D. A. Genov, G. Barta!, and X. Zhang, Three-dimensional optica l metamaterial with a negative refractive index, Nature 455 , 376 (2008). 25 U. Leonhardt and T. G. Philbin, General relativity in electrical engineering, New Journal of Physics 8 , 247 (2006). 26 (11 ) J. Yao, Z. Liu, Y. Liu, Y. Wang, C. Sun, G. Barta!, A. M. Stacy, and X. Zhang, Optical Negative Refraction in Bulk Metamaterials of Nanowires, Science 321, 930 (2008) . 23 UNCLASSIFIED/ ,CFOA OFFI&I.t.L l::ISE OHL¥
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