Cr3+-doped Mg4Ga4Ge3O16 near-infrared phosphor membrane for optical information storage and recording

A new near-infrared phosphor Mg₄Ga₄Ge₃O₁₆: Cr³⁺ with multi-photo-functionalities has been developed. Such phosphors can act as luminescent down-shifting materials converting UV and visible photons into NIR light (600–850 nm). UV irradiation induced strong NIR long persistent luminescence (LPL) can persist for more than 10 h. With the prolonged decay time, the extinguished NIR LPL can be rejuvenated by external photo stimulus including not only 980 nm light but also visible light. Such NIR photostimulated persistent luminescence (PSPL) presents separated write-in and read-out wavelength ranges. Meanwhile, photochromism (PC), that the material surface undergoes reversible change between white/pale green and ronbrown when triggered alternatively by UV and visible irradiation/heating, was also observed. Several recycle measurements demonstrate the robust fatigue resistance of PC property. Owning to the multi-photo-functionalities of Mg₄Ga₄Ge₃O₁₆: Cr³⁺, the fabrication of flexible phosphor membranes endows their application for optical information storage and repeatable optical recording. The electron motion in traps was studied by thermoluminescence (TL) and the color center formation was verified with electron spin resonance (ESR) spectra, based on which an energy level diagram was proposed for the illustration of the multifunctional mechanism. The revealing of multi-photo-functional mechanism and fabrication of flexible phosphor membranes may promote the development of a universal design principle for further study.