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 Dy 3+ and Ho 3+ ions into the BaSi 2 O 5 :Eu 2+ phosphor to adjust the distribution and depth of the trap centers. The generation of the pure phase BaSi 2 O 5 was confirmed by X-ray diffraction (XRD) and XRD Rietveld refinement . The peak emission of BaSi 2 O 5 : Eu 2+ phosphor is about 500 nm with 313 nm excitation. Both BaSi 2 O 5 : Eu 2+ , Dy 3+ , and BaSi 2 O 5 : Eu 2+ , Ho 3+ phosphors exhibit emission characteristics of Eu 2+ ions. The trap depths of the three phosphors are different by Gaussian fitting of thermoluminescence (TL) curves, and the depth of BaSi 2 O 5 : Eu 2+ , Dy 3+ phosphor can reach 1.070 eV. Typically, the flexible luminescent film based on BaSi 2 O 5 : Eu 2+ phosphor can be written optical pattern using 365 nm 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 BaSi 2 O 5 : Eu 2+ , BaSi 2 O 5 : Eu 2+ , Dy 3+ , and BaSi 2 O 5 : Eu 2+ , Ho 3+ phosphors, indicating the prospective use in optical information security.