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

• A composite metasurface comprising VO 2 and GST is presented as a platform for thermal information encryption. • Encrypted image and information can be revealed or concealed in response to a thermal stimulus. • The composite metasurface can be fabricated without complex lithographic processes. 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.