Study on the optical properties and broad infrared luminescence of Tm3+/Yb3+ co-doped Nb2O5-based glasses

Raman spectra of Tm3+/Yb3+ co-doped Nb2O5-based glasses with different Yb3+ concentrations have been studied. The results reveal that Yb3+ ions have no effect on the maximum phonon energy. Moreover, this heavy-metal oxide glass has low phonon energy with a value of ∼ 800 cm−1, which is very helpful to obtain strong infrared luminescence. The absorption coefficient of OH- group is small, which is helpful for infrared luminescence. Nb2O5-based glasses have a high refractive index with the nd value over 2. Yb3+ is not good for the refractive properties on the whole. The abbe number can be calculated by using characteristic values. All the glasses with different Yb3+ concentrations show high a Abbe number with the value over 16. Nb2O5-based glasses perform excellent optical properties that satisfy well the requirements of commercial glasses. The amorphous phase is confirmed by XRD and SEM images. Additionally, EDS results indicate the homogeneous distribution of compositions in the glass. A broad and strong near infrared emission centered at ∼ 1850nm ascribed to 3F4→3H6 is obtained from Tm3+/Yb3+ co-doped Nb2O5-based glasses at 980 nm excitation. The emission intensity first increases and then decreases with Yb3+. When y = 0.03, the emission is the strongest. The luminescence process is the energy transfer from Yb3+ to Tm3+. The lifetime of the excited state for Tm3+/Yb3+ co-doped Nb2O5-based glasses (y = 0.03) is calculated to be 2.292 ms. Such long lifetime is very favorable to get strong luminescence.