IR Image Encoding Uses Plasmonics

Researchers have developed an IR Image encoding method to hide information on the surface of a material using a plasmonic nanostructure so that it is only visible through an IR lens or camera tuned to the correct IR band.

Researchers demonstrated a method for hiding images within the IR spectrum in a study so that while visible in the IR, the same area appears as a solid color in the visible spectrum. To accomplish this, they created a dielectric layer with regularly spaced nanosize holes sandwiched between a reflective metallic mirror and a thin upper gold layer with holes corresponding to the discs in the middle layer. Using spun coat films of thermoplastic, they encoded images onto the surface of the plasmonic sandwich. They demonstrated that varying the diameters and depths of the holes could alter how different wavelengths of light reacted with the materials.

In a separate study, the researchers demonstrated that an infrared camouflage system could be used to erase and display an image in specific infrared bands. The researchers added a layer of phase change material (vanadium dioxide, or VO2) to its plasmonic sandwich. When the phase change was triggered, the VO2 layer dynamically changed the light reflecting from the surface from 100% to 0% and back. This technology could be used for anti-counterfeiting security, IR tagging, and/or IR camouflage.

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