A flexible metamaterial film created by researchers at the Technical University of Denmark (Lyngby, Denmark) and Boston University (Boston, MA) drastically reduces reflection of terahertz radiation, and can serve as a "stealth" material to minimize objects' radar cross-section at terahertz frequencies. The material was wrapped around a metallic cylinder for test, reducing the cylinder’s cross-section by close to 400 times at 0.87 THz.
The film consists of a 12-μm-thick polyimide (PI) layer, a 200-nm-thick layer of gold (Au), a second 12-μm-thick layer of PI, and a second 200-nm-thick layer of Au patterned by photolithography. The pattern is a periodic array of split-ring resonators with a unit cell size of 75 μm and a resonator side length of 54.5 μm. Total active area is 20 × 10 mm, spanned by two 10 × 10 mm inactive areas so the cylinder could be rotated to vary reflectivity. For radar tests, electro-optically generated terahertz pulses showed a reduction in cross-section by an average factor of at least 10 in the ±20° angular range. Contact Peter Uhd Jepsen at [email protected].