WO_x/Li⁺-Ag⁺/TiO₂ optoelectronic memory for holographic steganography

Holographic steganography is considered a highly secure information transmission method that relies on active optical media to achieve multifunctionality. Transition metal oxides undergo reversible color changes during photoelectrically driven cation migration, providing a platform for tunable holography. However, single-ion migration systems suffer from rapid attenuation of holographic fringe contrast under repeated electrical switching, leading to the loss of diffraction efficiency and hindering reliable information readout. In this Letter, we develop a WO_x/electrolyte/TiO₂ optoelectronic memory based on Li⁺-Ag⁺ dual-cation synergistic regulation. The excitation of near-ultraviolet coherent light not only constructs an initial hologram in the WO_x layer but also generates latent nucleation sites for Ag particles on the TiO₂ surface. During subsequent electrical switching, the dual-cation device can either hide holograms by modulating the Li⁺ ions distribution or reproduce signals by selectively depositing Ag particles on the pre-defined latent sites. The device integrates the color-changing pathway of WO_x/Li⁺ with the silver electrodeposition of TiO₂/Ag⁺, improving the diffraction efficiency and cycling durability. By programming specific voltage sequences, the holographic steganography based on spatiotemporal multiplexing is achieved. This work paves a bright path for high-density information security storage.