Dynamic optical information encryption strategy based on rare earth ions doped BaSi2O5 phosphors with adjustable trap distribution

Multi-modal strategies for optical information storage have received a lot of attention to meet the increasing security requirements. In this case, long persistent luminescence (LPL) phosphors with different dopant ions were obtained by introducing Dy3+ and Ho3+ ions into the BaSi2O5:Eu2+ phosphor to adjust the distribution and depth of the trap centers. The generation of the pure phase BaSi2O5 was confirmed by X-ray diffraction (XRD) and XRD Rietveld refinement. The peak emission of BaSi2O5: Eu2+ phosphor is about 500 nm with 313 nm excitation. Both BaSi2O5: Eu2+, Dy3+, and BaSi2O5: Eu2+, Ho3+ phosphors exhibit emission characteristics of Eu2+ ions. The trap depths of the three phosphors are different by Gaussian fitting of thermoluminescence (TL) curves, and the depth of BaSi2O5: Eu2+, Dy3+ phosphor can reach 1.070 eV. Typically, the flexible luminescent film based on BaSi2O5: Eu2+ phosphor can be written optical pattern using 365nm ultraviolet (UV) light, such as "DL" and "fireworks" patterns, and subsequently read out by thermal or infrared light stimulus. Further, a strategy for encryption and decryption of dynamic optical information in Morse code has been developed using BaSi2O5: Eu2+, BaSi2O5: Eu2+, Dy3+, and BaSi2O5: Eu2+, Ho3+ phosphors, indicating the prospective use in optical information security.