Comparison of Glass Material and Laser Excitation Regime for Upconversion‐Based 3D Volumetric Display

Two‐step, two‐frequency (TSTF) upconversion in rare‐earth‐ion (REI) doped solids is a proven strategy for achieving 3D volumetric displays, with potential applications in defence, healthcare, education, manufacturing, and entertainment. Early studies have primarily focused on REI‐doped fluoride glasses or single crystals, which efficiently support TSTF upconversion due to their low‐phonon energy. However, these materials are challenging to produce at the size and quality required for commercial applications. This study explores tellurite and germanate glasses as scalable, low‐phonon‐energy alternatives by benchmarking their TSTF upconversion performance against fluoride glass for Er 3+ green fluorescence. Tellurite and germanate glasses exhibit dimmer green upconversion under continuous‐wave excitation, while tellurite glass unexpectedly outperforms fluoride glass when both lasers are pulsed with properly adjusted modulation parameters. Rate equation‐based simulations are used to explain these findings. In particular, tellurite glass exhibits brighter emission than fluoride glass under synchronized dual‐pulsed excitation due to its much higher ground‐ and excited‐state absorption cross sections and radiative decay rate, which compensate for its shorter 4 S 3/2 lifetime. Green voxel generation is demonstrated in a large ≈4 × 4 × 4 cm 3 Er 3+ ‐doped tellurite glass cube with high optical quality. These results open new directions for REI‐doped glass development and laser design for TSTF upconversion‐based 3D volumetric displays.