Blue Upconversion Emission of Nd3+/Tm3+/Yb3+ Triply Doped Aluminophosphate Optical Fibers

Glasses containing rare-earth ions (RE3+) for upconversion (UC) luminescence have been widely explored in several photonic applications. Materials containing Tm3+ present an intense blue emission when excited in the near-infrared range, allowing them to be used as solid-state lasers and other emitter devices. Tm3+ are generally combined with other RE3+ to improve the UC efficiency; however, increasing the number of dopants can be an issue for their solubility in the glass matrix and for fiber drawing. In this work, alkali-aluminum-phosphate glasses, a host matrix with high RE3+ solubility and fiber-drawing ability, were produced containing different amounts of Tm3+, Nd3+, and Yb3+, as well as the respective tridoped optical fibers. Glass samples containing RE3+ were excited at 808 and 980 nm to evaluate the mechanism involved in the luminescence process. In addition, triply doped optical fibers were excited at 788 and 980 nm, and a bright blue luminescence was observed at both wavelengths. Thus, due to the intense UC emission measured on RE3+ triply doped optical fibers with low optical loss, the developed material presents great potential for fiber-based photonic applications.