Non-volatile and Secure Optical Storage Medium with Multilevel Information Encryption

Non-volatile photomemory based on photomodulated luminescent materials offers unique advantages over voltage-driven memory, including low residual crosstalk and high storage speed. However, conventional materials have thus far been volatile and insecure for data storage because of low trap depth and single-level storage channels. Therefore, the development of a novel non-volatile multilevel storage medium for data encryption remains a challenge. Herein, a robust, non-volatile, multilevel optical storage medium is reported, based on a photomodulated Ba₃MgSi₂O₈:Eu³⁺, which combined the merits of light-induced valence (Eu³⁺ → Eu²⁺) and photochromic phenomena using optical stimulation effects, accompanied by larger luminescent and color contrasts (>90%). These two unique features provided dual-level storage channels in a single host, significantly improving the data storage security. Notably, dual-level optical signals could be written and erased simultaneously by alternating 265 and 365 nm light stimuli. Theoretical calculations indicated that robust color centers induced by intrinsic interstitial Mg and vacancy defects with suitable trap depths enable excellent reversibility and long-term storage capability. By relying on different luminescent readout mechanisms, the encrypted dual-level information can be accurately decrypted by separately probing the Eu²⁺ and Eu³⁺ signals, thus ensuring information security. This study proposes a novel approach for constructing multilevel information storage channels for information security.