Refractive‐Index‐Matching‐Based Encryption of Photonic Crystal Prints with Multistage and Reconfigurable Information

Abstract Encryption of photonic prints with multiple information is highly desired due to their potential applications in high security of anticounterfeiting and information protection. Here, a new refractive‐index‐matching‐based technology is developed to construct encrypted photonic crystals (EPCs) with multistage and reconfigurable information by introducing solvents with different refractive indexes into PCs. The multilevel information of the EPCs can be hidden at normal conditions since the similar refractive index between the PC and solvent induces the diminishment of the structural color of the EPC. Programmable showing of multistage information can be realized by simply heating EPCs for different times owing to the diverse evaporation rate of the solvents. The switch of the EPCs between the encryption and decryption states is fully reversible. Based on these unique characteristics, the information of EPCs can be reconfigured repeatedly by rational design and choosing of solvents. This work paves a new way in the fabrication of EPCs with multilevel and reconfigurable information and will promote their applications in displays, printing, and anticounterfeiting.