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Covert Infrared Image Encoding – Hiding In Plasmonic Sight

Plasmonic materials can uniquely control the electromagnetic spectrum due to nano-scale surface architecture. Recent advances in nanotechnology and materials science and their combined capacity to develop controlled geometries at the nano-scale continue to evolve, as observed with optical properties of amplitude, phase and wave fronts for materials in optics. Although researchers have focused on individual frequencies and wavelengths, few studies have attempted to control fundamental properties across multiple electromagnetic frequency regimes. For instance, multispectral systems can establish new surfaces with combined functions, such as reflective multilayers that selectively absorb and emit infrared light in transparent atmospheric windows for thermal management. Similarly, plasmonic filters with tunable resonance can be used for multispectral color imaging. These concepts can be applied to achieve camouflage and anti-counterfeiting techniques.

Resonances in such systems occur as excited electric and magnetic multipole modes that depend on the geometries and dimensions of constituent materials due to inherent features of plasmon hybridization and plasmon-phonon-coupling. Such traits can be effectively used to engineer optical surface properties of a material. However, attempts to control structural parameters and accommodate a specific spectral regime can influence higher-order resonances in lower-wavelength ranges, resulting in a lack of independent control of optical character in specific spectral regions.

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