Improved 2∼5 μm mid-infrared fluorescence through energy transfer processes in Er3+/Ho3+ co-doped fluoride glasses

In this paper, Er 3+ /Ho 3+ co-doped fluoride glasses were prepared by the high temperature melt-quenching technique. Pumped by the 980 nm LD , as a result of the emission spectra overlapping of Er 3+ and Ho 3+ ions, a broadband mid-infrared emission band from 2530 to 2950 nm with a full width at half maximum of the synthetic fluoride glasses near 231 nm was obtained, which exist latent application in wide band tunable mid-infrared fiber laser. Furthermore, the intense 4.1 μm mid-infrared fluorescence (3600–4400 nm) was obtained and the FWHM was 320 nm. The up-conversion emission peaks around 525, 546 and 660 nm, near-infrared emissions at 1.2 and 1.5 μm together with mid-infrared fluorescence around 2.0 μm was observed in Er 3+ /Ho 3+ co-doped fluoride glass. Moreover, the relevant energy transfer processes were discussed in detail based on the emission spectrum and the energy level transition processes. The results indicate that the fabricated Er 3+ /Ho 3+ co-doped fluoride glasses exist prominent emission features for fiber laser gain medium.