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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.
UNCLASSIFIED/ ,'FOR: OFFl@IAL l!ISI!!! 9HLY Figure 10. Light Waves at Cloaking Device. Wave propagation in (a) virtual space and (b) real space . This idea of cloaking by coordinate transformations was put forward by two independent groups. Their theories appeared in Science Express on 25 May 2006 and were published back to back in Science magazine later on. The first paper9 only considered isotropic materials, optical materials where the speed of light at each point is the same in each direction but may vary from point to point. Most natural optical materials, except for some crystals and all liquid crystals, are isotropic. In isotropic materials, invisibility is perfect only for light rays, but the cloaking device may cause dislocations of lig ht waves. In addition to the optical implementation of coordinate transformations, some other tricks are required. The second paper10 considered anisotropic materials for cloaking or other manipulations of electromagnetic waves. Here, perfect invisibility is possible in principle (but not in practice, as is discussed later). I n October 2006, the first cloaking device was demonstrated, 11 for microwaves. Science magazine regarded cloaking as one of the top 10 science breakthroughs of the year (it was top in physics and engineering) . Scientific American listed the inventors of cloaking devices-Sir John Pendry, David Smith, David Schurig, and Ulf Leonhardt among the top 50 policy, business, and research leaders of the year. The first paper12 on cloaking had initially been rejected by most major science and physics journals before it finally appeared in Science, but since 2006, cloaking has become a mainstream subject on which about a thousand papers have been published so far. Metamaterials The first prototype13 of a cloaking device was designed to operate in the microwave region of the electromagnetic spectrum, for a wavelength of about 3 cm. The device consists of 10 rings of flexible circuit board. The copper of the circuit board has been etched away, apart from characteristic structures of about 3-mm size, so-called split ring resonators. UNCLASSIFIED//509 OFFICIOP 1!55 ODtf PX 9
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 29 pages are in the text index: search them above, or from the library's search.