Fig. 1: Demonstration of the optical information storage using storage phosphors.

The left panel illustrates the writing mechanism, encompassing phosphor charging through optical excitation and trap filling. Beyond the conventional charging method via direct photoionization (solid arrow), an alternative approach, up-conversion charging (UCC), which involves two-step ionization (dashed arrows), can also be employed to write information into the phosphor medium. The right panel illustrates the readout mechanism, which operates on the principles of thermal- or photo-stimulated luminescence, involving the release of trapped charges and the subsequent emission from the emitting ion