A new coding-decoding system through combining near-infrared photonic crystals and their spatial reflection spectra

Developing new photonic coding technology is important and highly desired due to its potential applications in information protection and communication. Here, a new coding-decoding system was established through combining the line coding of near-infrared photonic crystals (NIRPCs) with diverse reflection wavelengths and their spatial reflection spectra (SRS). The line coding was realized by the arrangement of soft, flexible and tailorable NIRPC films which were fabricated through the self-assembly of silica particles into poly(ethylene glycol) phenyl ether acrylate (PEGPEA). The information of the line coding was well hidden under ambient circumstances, benefiting from the similar colors of NIRPCs, but could be revealed by its SRS pattern. Different from the complex fabrications required for previous coding systems, the coding process is considerably simple and efficient, and tens of thousands of combinations of line coding can be generated in principle. Additionally, elaborate line coding was further achieved by the introduction of the codes of dual layers. The reflectance of the upper/bottom layer of the code depends on its stacking order due to the blocking effect, resulting in more intricate line coding. This newly developed coding-decoding system offers the extended applications of PCs in anticounterfeiting, information protection and communication. A new coding-decoding system was established through combining the line coding of near-infrared photonic crystals (NIRPCs) with diverse reflection wavelengths and their spatial reflection spectra (SRS).