Thermal information encryption based on composite metasurfaces comprising volatile and nonvolatile phase-change materials

With the advent of immense data growth, information encryption has garnered significant attention. Encryption based on the control of thermal emission is a promising alternative to optical encryption systems, because it allows for the straightforward decoding of encoded information under an infrared camera while maintaining high resistance against replication. This study presents a thermal encryption system based on composite metasurfaces comprising VO 2 and Ge 2 Sb 2 Te 5 (GST), which are volatile and nonvolatile phase-change materials, respectively. Although individual phase-change materials have limitations and advantages as material platforms for thermal encryption, this composite metasurface integrates VO 2 and GST into a single functional platform, thereby combining the beneficial features of both materials. The multiple crystallization states of GST enable high-density information to be encoded into the metasurface, while the temperature-driven dynamic phase switching of VO 2 allows the encrypted images or digital information to be revealed or concealed in response to a thermal stimulus. Additionally, the VO 2 -GST composite metasurface does not require complex fabrication processes such as photolithography and electron-beam lithography. This study provides a novel architecture for high-density and robust thermal information encryption and can also be leveraged in future designs of reconfigurable and intelligent thermal metasurfaces.