Colored, Covert Infrared Display through Hybrid Planar-Plasmonic Cavities

Abstract

Artificial covert infrared (IR) displays have recently emerged as an anti-counterfeiting method for spontaneous thermal emissive surfaces and optically encoded information. However, the unnatural appearance of a conventional thermal emissive label in the visible region limits the widespread application of an artificial covert IR display. This paper presents a colored, covert IR display exhibiting visible color patterns and thermally encoded data simultaneously based on a hybrid planar-plasmonic cavity (HPPC). The HPPC is composed of two spectrally distinguished resonant structures: 1) an ultrathin planar cavity with an amorphous silicon (a-Si) layer on gold (Au) for visible coloration and 2) an IR plasmonic cavity with hole-patterned Au on a polymer substrate with a back mirror for thermal data encoding. Such hybridization of multi-band resonance can not only enhance the vivid coloration but also enhance the data storage capacity per unit. Camouflage labels with encrypted thermal data are successfully demonstrated for practical applications using a flexible HPPC. Collectively, the proposed HPPC enables a new type of anti-counterfeiting method that achieves both esthetic, visibly encoded data, and covert, thermally encoded data.