Research Progress on Rare-Earth-Doped Ultraviolet Upconversion Materials and Lasers

Rare-earth ions with unique stepped energy levels have attracted considerable attention in the field of upconversion luminescence. Rare-earth-doped ultraviolet upconversion materials are effective in realizing ultraviolet shortwavelength compact lasers. However, substantial energy loss occurs in the ultraviolet upconversion process of rare-earth ions, resulting in extremely low ultraviolet upconversion efficiency. Therefore, manufacturing high-power ultraviolet upconversion lasers is difficult, and the practical application of ultraviolet upconversion lasers is limited. By reducing the matrix phonon energy, regulating the matrix microstructure, improving the pumping mode, and adjusting the laser resonator morphology, energy transfer during ultraviolet upconversion can be effectively regulated and the efficiency of ultraviolet upconversion laser can be improved. In this study, the principle of upconversion luminescence, composition of ultraviolet upconversion materials, strategies for enhancing ultraviolet upconversion luminescence, and recent advances in ultraviolet upconversion lasers are reviewed.