Switchable active phase modulation and holography encryption based on hybrid metasurfaces

Metasurfaces are planar devices containing delicately designed nanoantenna or resonator arrays that allow for beam shaping, super resolution imaging, and holography. Hybrid metasurface – by integrating with tunable materials such as two-dimensional materials and phase change materials (PCMs) – provides a potential platform for active modulation of wavefronts. Specifically, PCMs can flexibly switch between crystalline and amorphous states with nonvolatile property under external stimuli and provide a large refractive permittivity contrast. Using metasurfaces based on PCM to manipulate wavefronts may provide new opportunities for switchable functionalities. Here, we propose two types of metasurface devices based on whole PCM films to realize switchable holography and simultaneous phase and interference encryption. This feature can be used to encrypt information in a switched state and store camouflage information in the other state by simply applying external thermal stimuli to the entire metasurface. This method can be applied in areas such as beam shaping, optical encryption, and anti-counterfeiting.