Single mode green lasing and multicolor luminescent emission from an Er³⁺-Yb³⁺ co-doped compound fluorosilicate glass microsphere resonator

Enhanced upconversion lasing and luminescence is obtained in a transparent compound fluorosilicate glass co-doped with Yb³⁺ and Er³⁺ ions. The sample is prepared by a conventional melt-quenching technique followed by a heat treatment, and a very high upconversion efficiency (quantum yield >1%) is achieved. The physical processes involved start from a phase-separated, as-melt fluorosilicate glass consisting of fluorine-rich domains, which provide the low phonon energy environment for Er³⁺ ions. In addition, visible green lasing in a microsphere resonator with a diameter of 58 μm is observed with a relatively low lasing threshold of circa 52.5 μW. Importantly, when the input power increases to 16.8 mW in a microsphere with a diameter of 110 μm, the colors of the luminescent emissions became yellow-green and then yellow-red when the pump power is increased further to 40 mW. This presents a significant improvement in the development of visible light sources for microphotonics applications.