Nonvolatile phase-state-gated OAM metasurface holography for dual-key access

Abstract

Orbital-angular-momentum (OAM)-selective metasurface holography offers a promising route for spatial-mode encryption, but purely modal multiplexing is often limited by intermodal leakage, increased sampling demands, and static channel access. Here, we demonstrate a nonvolatile phase-state-gated OAM meta-hologram based on Sb2S3, where the amorphous/crystalline end point state serves as a persistent material-state key and the incident (ℓ, M) structured beam serves as an optical key. A holographic channel is reconstructed only when both keys are simultaneously matched. To overcome the state-dependent phase-efficiency mismatch of Sb2S3, end point-specific meta-atom libraries and pixel-wise joint layout optimization are used to encode two state-dependent holographic responses into one static metasurface. At 680 nm, the device realizes four selectively addressable channels from two mode keys and two nonvolatile end point states, with end point reconstructed-image normalized cross correlation values ranging from 0.84 to 0.89. Channel selectivity is quantified using a fixed-window normalized cross correlation matrix, where each experimental reconstruction is compared with all four target patterns within the same evaluation window. Intermediate crystallization levels produce hybrid reconstructions due to end point-library mismatch, indicating that reliable multilevel expansion requires dedicated state-specific libraries and encodings. This work extends OAM meta-holography from purely optical modal multiplexing toward nonvolatile material-state-gated access, offering a compact platform for dual-key optical encryption and reconfigurable holographic displays.