3.9 μm emission and energy transfer in ultra-low OH−, Ho3+ /Nd3+ co-doped fluoroindate glasses

Ho3+/Nd3+ co-doped fluoroindate glass samples were prepared by melt-quenching. The absorption and emission spectra, and the differential scanning calorimetry (DSC) curve were measured and used to evaluate the spectroscopic parameters and thermal properties. An intense ~3.9 μm emission, ascribed to the transition Ho3+:5I5 →5I6, was observed under the excitation of an 808 nm laser diode and was ascribed to the efficient energy transfer process from Nd3+: 4F3/2 to Ho3+: 5I5, showing the Nd3+ role as a sensitizer. The optimal concentration ratio of Ho3+ and Nd3+ for ~3.9 μm emission was estimated to be 1:1. The spectroscopic performance suggests that the Ho3+/Nd3+ co-doped fluoroindate glass is a potential gain material for ~3.9 μm laser applications.