Non-volatile and switchable encrypted metasurface for simultaneous nanoprinting and holography

Metasurfaces possess the ability to manipulate wavefront of light at sub-wavelength scales, enabling flexible multi-functional integrations, such as simultaneous nanoprinting and holography. However, previous near-field nanoprinting and far-field holographic technologies present limitations in terms of dynamic switching and flexible tunability. Here, we propose an optical encryption scheme based on non-volatile and switchable metasurface with low-loss phase change material Sb2Se3 that allows active manipulation of both the amplitude and the phase. A modified Gerchberg-Saxton algorithm is developed to achieve near-field amplitude and far-field phase distributions, and anisotropic Sb2Se3 nanobricks act as dynamic meta-atoms for amplitude and propagation phase modulation. In particular, the simulation results show that the dynamic switching for near-field nanoprinting patterns and far-field holographic images can be achieved by controlling the polarization states of the incident light, the imaging distance, as well as different crystallization level of Sb2Se3. The metasurface with two-level encryption mode effectively enhances the information storage capacity and encryption security level by utilizing the active modulation characteristic of Sb2Se3. Such scheme has potential applications in secure communications, dynamic image displays, and high-capacity information storage.