2.8 μm emission and OH quenching analysis in Ho doped fluorotellurite-germanate glasses sensitized by Yb and Er.

The use of Yb and Er co-doping with Ho to enhance and broaden the Ho: I → I ~2.8 μm emissions are investigated in the fluorotellurite-germanate glasses. An intense ~3 μm emission with a full width at half maximum (FWHM) of 245 nm is achieved in the Er/Ho/Yb triply-doped fluorotellurite-germanate glass upon excitation at 980 nm. The glass not only possesses considerably low OH absorption coefficient (0.189 cm), but also exhibits low phonon energy (704 cm). Moreover, the measured lifetime of Ho: I level is as high as 0.218 ms. In addition, the energy transfer rate to hydroxyl groups and quantum efficiency (η) of I level were calculated in detail by fitting the variations of lifetimes vs. the OH concentrations. The formation ability and thermal stability of glasses have been improved by introducing GeO into fluorotellurite glasses. Results reveal that Er/Ho/Yb triply-doped fluorotellurite-germanate glass is a potential kind of laser glass for efficient 3 μm laser.