Improving the Two-Step Two-Frequency Upconversion Luminescence of Er3+ in 70teo2–20zno–10geo2 Glass Ceramic by Doping CaF2

The investigation of efficiency enhancement in TSTF UCL materials through near-infrared (NIR) light excitation has important implications for volumetric three-dimensional (3D) imaging. Here, we developed the TSTF UCL process of the tellurite glass 70TeO2-20ZnO-10GeO2 doped with Er3+ and CaF2. Under dual-mode excitation with 1550 nm and 850 nm NIR lasers, a strong photon-excited synergistic effect was exhibited in these glass ceramics. Through the UCL spectra analysis, it can be found that CaF2 plays an important role in improving UCL intensity. The optimized glass ceramics are selected and a simple optical display system is designed to achieve a good 3D volumetric imaging effect. Moreover, we levitate the 3D image in the air using a levitation display technology, which can be utilized to display and distinguish objects in medicine, military, or commercial applications. Such an improving TSTF UCL intensity strategy by doping fluoride nanocrystals is generally applicable for many other glass ceramics.