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This Defense Intelligence Reference Document, DIA-08-1004-006, is dated 6 April 2010 and was prepared by the Defense Intelligence Agency's Defense Warning Office. It is one of a series of advanced technology reports produced in FY 2009 under the Advanced Aerospace Weapon System Applications Program. The report reviews electromagnetic and optical metamaterials and their uses in sub-diffraction imaging, component miniaturization, energy harvesting, optical isolators and tunable devices. It concludes that metamaterials remain academic but have great potential for aerospace applications.
From the source:Release of 2026-09-18 Incident: 4/6/10, 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 metamaterials, engineered structures designed to control electromagnetic waves in ways ordinary materials cannot, and argues that their main aerospace value lies in unusual optical and microwave properties together with significant component miniaturization. The report reviews possible applications including sub-wavelength imaging, compact waveguides and lasers, energy harvesting, tunable absorbers, nonreciprocal devices, and switchable materials, with particular emphasis on infrared and microwave uses for sensing, power management, and payload efficiency. It notes that many of the most ambitious applications depend on the practical output of a still-nascent field, especially in optical metamaterials, where only limited demonstrations had been achieved and fabrication remained a major constraint. The document presents metamaterials as a promising advanced materials field with credible niche applications and broader long-term potential.
UNCLASSIFIED/ /POil Offl@IAI:: YS& 8Nl::\f One possible design for the microwave frequency band is shown in Figure 17. High absorption is accomplished by reducing reflections to zero. This is accomplished by choosing metamaterials parameters such that &eri@,.) = μ.1i@,. ) at the resonant frequency co,. . Note that both the real and imaginary parts of the permittivity and permeability must be equal to each other, and that the imaginary parts don't necessarily need to be small for absorber applications. In fact, it is desirable that they are not too small, thereby enabling 100 percent absorption within a single layer of metamaterial. The above design can be scaled down to the THz range, as was later demonstrated in Reference 34. It is difficult to find strongly absorbing materials at THz frequencies that are compatible with standard photolithography. Thus, a potential application of these metamaterial structures is as absorbing elements in thermal detectors. A strong absorption coefficient is also necessary to have a small thermal mass. This is important for optimizing the temporal response of therma l detectors. The metamaterial presented here has a 6 micron thick film (that is, )\/50 thickness for THz radiation) and 70 percent absorptivity, which yields an absorption coefficient of 2000 cm- 1 . One drawback of the original design was the narrow angular range of the absorber. The absorption dropped dramatically when the incidence angle was as small as 20 degrees. The reason for that is a relatively large unit cell of the metamaterial. In fact, when the unit cell size is larger or comparable to )IJ2n, where n is the refractive index of the substrate, it is inappropriate to call such structure a "metamaterial". A true impedance matched metamaterial would, in fact, always have a very broad angular response. ' .' . H' .--- - --- - --- -- - •-- - --- - ------- - •------ X . ' ' ! 0.8 --------------- 1--------------- 1---------------: . ' ~-6--------------- i -------------+-------------- -0.4 -- --------- ---- [ ---------------; ____ _________ __ PIMNIM Lx0.2 L x = c,J .E=J.L=-1 +i L=200nm ,i::=1-L=-1 +i 10 20 30 40 Figure 19. Wide-Angle Plasmonic Absorber Based on Negative Index Metamaterial. Right panel: schematic of an absorption-measuring experiment. A generic metamaterial with 8 YY = f.l zz = - 1+i, f.lx., = l is assumed . Left panel : angular dependence of the absorption for a generic and specific (shown in the inset) metamaterial. Both exhibit wide-angle absorptivity. (Reference 20) This fact can be expressed by a simple formula for the absorption coefficient A (Reference 20): UNCLASSIFIED/fFOA OFFICilial.L. W&li OlhlL.¥ 21
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Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 38 pages are in the text index: search them above, or from the library's search.