Dynamically programmable GST-based metasurface for multi-channel holography and optical encryption.

This study demonstrates a dynamically programmable metasurface leveraging germanium-antimony-tellurium (GST) for multi-channel holographic and optical encryption. By integrating a GST thin film with gallium arsenide nanostructures, non-volatile switching between near-field reflection and far-field diffraction modes is achieved via reversible GST phase transitions. Under y-polarized illumination in the crystalline state, the metasurface produces near-field amplitude-encoded images ("A", "B", "C") at wavelengths of 400 nm, 600 nm, and 800 nm. Conversely, under x-polarized illumination in the amorphous state, it projects far-field phase-modulated holograms ("X", "Y", "Z") at 1064 nm, 1450 nm, and 1550 nm. By leveraging wavelength, polarization, and GST phase state, a nested encryption architecture is established that dynamically associates code-chips to map plaintext to ciphertext, thereby substantially enhancing security. This work offers a promising strategy for high-capacity, reconfigurable optical encryption with potential in secure communications and dynamic displays.