Effect of the phosphate content on the spectroscopic and lasing properties of Er3+/Yb3+-doped fluorophosphate glasses

The influence of phosphate content on the formation and luminescent properties of Er3+/Yb3+-doped fluorophosphate glass has been studied. Using the Judd-Ofelt theory the phenomenological intensity parameters Omega(t) (t = 2; 4; 6) were obtained. The change of Judd-Ofelt parameters indicates minor differences in Er3+ environment with increase in the phosphates content up to 10 mol.%. It was shown that in the studied fluorophosphates glasses erbium ions remain in the fluoride environment. The increase in phosphate content leads to lifetime change of erbium laser level from 9.4 ms to 7.8 ms. Using the Judd-Ofelt intensity parameters Omega(t), the stimulated emission cross-section of the I-4(13/2)-> I-4(15/2) transition has been calculated. The gain shape of the glasses with lower (2-10 mol. %) phosphate content has been found to be smoother than for phosphate glasses with 20 mol.% Ba(PO3)(2), which makes former very attractive gain material.