Narrowband Metamaterial Absorber for Terahertz Secure Labeling
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Flexible metamaterial films, fabricated by photolithography on a thin copper-backed polyimide substrate, are used to mark or barcode objects securely. The films are characterized by continuous-wave terahertz spectroscopic ellipsometry and visualized by a scanning confocal imager coupled to a vector network analyzer that constructed a terahertz spectral hypercube. These films exhibit a strong, narrowband, polarization- and angle-insensitive absorption at wavelengths near 1 mm. Consequently, the films are nearly indistinguishable at visible or infrared wavelengths and may be easily observed by terahertz imaging only at the resonance frequency of the film.
KeywordsMetamaterial Terahertz imaging Ellipsometry Labeling
This work was supported in part by the U. S. Army Research Laboratory and the U. S. Army Research Office through the Institute for Soldier Nanotechnologies, under contract number W911NF-13-D-0001, and Triton Systems Internal Research and Development Program 1500-197. The authors wish to thank John Blum for his contributions to alternative fabrication methodologies.
A video version of the terahertz hypercube images, sweeping through the hyperplanes one frequency at a time, can be viewed in the supplement.
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