Optical transition properties of Yb3+ in new fluorophosphate glasses with high gain coefficient

A new series of 0.4MgF2-0.4BaF2-0.1Al(PO3)3-0.1Ba(PO3)2 glasses doped with Yb3+ is introduced for fiber and waveguide laser applications. Spectroscopic properties including emission cross-section and lifetime and optical properties including refractive index, nonlinear refractive index, and Abbe number are reported as a function of Yb2O3 concentration. The refractive index nd is linearly dependent on Yb2O3 concentration, while the nonlinear refractive index, n2 = 1.42 × 10−13 esu, which is independent of Yb2O3 concentration, is extremely small. In addition, the Abbe number is remarkably high, >65, and is also independent of Yb2O3 concentration. To our knowledge, the emission cross-section σemi, which was found to be ∼0.87 pm2 at the lasing wavelength of 996 nm, is the highest one among fluorophosphate glasses. This glass exhibits an extremely high gain coefficient, G = 0.95 ms pm4, and high quantum efficiency of η = 94%. The combination of outstanding spectroscopic (high emission cross-section and gain coefficient) and optical (low dispersion and small nonlinear refractive index) properties demonstrates that the current Yb3+ activated fluorophosphate glass is an excellent candidate material for fiber and waveguide lasers.