Multifunctional photochromic CaLuGaO4:Bi3+,Er3+ phosphors for advanced optical anti-counterfeiting and rewritable information storage applications

Traditional optical anti-counterfeiting materials suffer from the static and simplistic optical responses, rendering them vulnerable to replication and constraining practical utility. Addressing these challenges, the strategic design of multifunctional materials with tunable and dynamic optical properties offers a promising route to advanced, reliable, resilient anti-counterfeiting and rewritable information storage technologies. Herein, we report Bi 3+ and Er 3+ co-doped CaLuGaO 4 phosphor exhibiting multicolor luminescence, afterglow, and reversible photochromism. Emission color is tunable between blue and cyan by altering ultraviolet excitation wavelength or temperature, while up-conversion luminescence shifts from yellow-green to green with increased 980 nm excitation power or reduced irradiation distance. Additionally, Bi 3+ doping induces defect-associated blue afterglow and photochromic switching under 254 nm light, reversible by heat treatment or 395 nm light irradiation. These multifunctional features enable sophisticated anti-counterfeiting and encoded information storage, positioning CaLuGaO 4 :Bi 3+ ,Er 3+ as a next-generation smart optical material.