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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/;'fOll Offl@lsltt HS! OHLY room temperature radiates 460 W. Earth-based powerful mid-infrared sources can be used for nighttime powering of airborne platforms. All these applications would benefit from the following components: (a) perfect absorbers of infrared radiation that can be installed on the receiving platforms, (b) efficient sources of thermal mid-infrared radiation. These two components are related to each other. Therefore, developing an ultra-thin perfect absorber of infrared radiation would be highly desirable. The ultra-thin aspect is important because it enhances the radiation-to-electricity conversion efficiency. For example, it is well known that carrier separation -collection efficiency in a solar cell improves as the cell gets thinner. The challenge is to combine this carrier separation-collection efficiency with sufficient absorption. Unfortunately, the absorption length of many sem iconductors in the infrared is fairly small. Recent experiments provide the new metamaterials-based concept for increasing the absorptivity of otherwise semi-transparent materials. Below some of the (still unpublished) experiments and theoretical developments that might result in new metamaterials-based perfect absorbers are described. Figure 20 (left) indicates a very instructive experimental result: reflectivity R from an ultra-thin (500 nm) SiC film backed up by a metal mirror. At w = 762 cm- 1 (or 'A = 13.1 μm) reflectivity from the structure is less than 3 percent. That implies 97 percent absorption in a film of thickness d = 'A/25 . This remarkable absorptivity can be explained using the well-known microwave concept: the Salisbury screen. It turns out that at 'A = 13.1 μm film thickness is d = 'A/4n, where n = n,.e + in;111 is the complex refractive index of SiC. A simple formula for the reflectivity from a metal-backed thin film can be derived: 2r, _ e2;0 0R -_1.....::....--2;,5-1 (5) 1- r0e where r0 = n - l is the reflection coefficient from the air/SiC interface and 5 =nf<od is the n+l complex phase shift across the film which includes losses. Fixing the laser frequency w =cf<o and the sample's thickness d, we can plot the reflectivity as a function of re(n) and im(n). As can be clearly seen from Figure 20 (right), there is a "sweet spot" correspond ing to specific values of re(n) and im(n) that results in vanishing reflectivity (or perfect absorption). R vanishes when the quarter-wavelength condition is approximately satisfied: re(n)k0d =(2m+l)/2 (6) where mis an integer. Finite reflection and imperfect absorption result from lower (or higher) values of im(n), Note that, coincidentally, for the case of heavily doped SiC predicted reflection is only 3 percent. However, for most materials (that is, Si for visible light) absorption is too low for perfect absorption. Therefore, a question is posed: Can one modify the structure of the metal screen to enhance absorption? It is CM Ms that enable such functionality? UNCLASSIFIED//FOR QFFI€ililik HS! OHL I 24
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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.