Fig. 4: Examination of the storage capability and rewritability of the Gd₃Ga₅O₁₂:Cr³⁺ phosphor.

a Thermoluminescence curves acquired following UCC with a 450 nm laser at −196 °C. The dashed curve depicts data recorded after a 10-s delay, while the solid line represents data collected after a 120-h delay at room temperature. b, Evaluation of trap depth through thermoluminescence measurements conducted at various heating rates from 0.25 to 4 °C·s⁻¹, as depicted in the inset, revealing trap depth of 1.55 eV according to Hoogenstraaten’s method. c Repeatability experiments involving cycles of UCC and thermal bleaching to demonstrate the reusability of the phosphor for storage purposes. The trend of afterglow intensity indicates negligible reduction in storage capacity even after 50 cycles. The inset visually illustrates this reusability, displaying afterglow images captured during each cycle. These images feature red numerical values corresponding to afterglow emissions from patterns written on the phosphor using the 450 nm laser engraver. Each red number denotes a specific instance of recycling on the same phosphor. Notably, the imaging data differs from the spectral intensity measurements, as the latter employs a uniform laser and spot size. The images were captured using a digital camera with a 0.6-s shutter speed