Strong and broadband 2.7 μm fluorescence of Yb3+/Er3+ co-doped ZnO modified tungsten tellurite glasses for broadband mid-infrared optical amplifiers and tunable fiber lasers

Strong and broadband 2.7 μm fluorescence with effective emission linewidth of 140.4 nm has been achieved in 1 mol% Yb2O3 and 1 mol% Er2O3 co-doped ZnO modified tungsten tellurite glass under an excitation from a 980 nm laser diode. The influences of Yb3+ concentration on 2.7 μm spectroscopic properties of Yb3+/Er3+ co-doped ZnO modified tungsten tellurite glasses were analyzed by absorption spectra, emission spectra and lifetime measurement. Long lifetime of 4I11/2 level (649.4 μs), high spontaneous radiative transition probability (65.1 s−1), large emission cross section (8.27 × 10−21 cm2) and figure of merit (5.37 × 10−24 cm2s) near 2.7 μm ensure intense 2.7 μm emission. Furthermore, the energy transfer coefficients between Yb3+ and Er3+ ions are quantitatively determined to explain the reinforcement of 2.7 μm fluorescence. Therefore, Yb3+/Er3+ co-doped ZnO modified tungsten tellurite glasses with better 2.7 μm spectroscopic performances are predominant candidates in constructing broadband mid-infrared optical amplifiers and tunable fiber lasers.