Enhanced mid-infrared emission by energy transfer in Er3+/Yb3+ co-doped zirconium fluoride-chloride transparent glass

Transparent Er3+/Yb3+ co-doped zirconium fluoride-chloride (ZFC) glass are firstly prepared for mid-infrared emission. The stronger 2750 nm emission from Er3+: ZFC glass is owing to a stronger covalence and local asymmetry of the crystal field around the Er3+ ions. The low phonon energy (600 cm−1) of ZFC glass are calculated from FTIR spectra and confirmed by Raman spectra. The low OH− concentration (9.75 × 10−17 cm−3) and high transmittance (1300-4000 cm−1) of ZFC glass are beneficial to mid-infrared emission. Co-doping rare earth ions Yb3+ enhances the 2750 nm emission. The energy transfer process between Yb3+ and Er3+ are identified based on luminescence spectra and decay curves. The role of Yb3+ plays the sensitizer on Er3+: 4I11/2 and enhances the excited state absorption of Er3+: 4I13/2 → 4F9/2, which is good for transition Er3+: 4I11/2 → 4F13/2. Thus, Er3+/Yb3+: ZFC glass with large emission cross section (1.06 × 10−20 cm2) is a potential laser application material.