Alkali-metal-free phosphate glass with dn/dT≈0 for use in fiber amplifiers

摘要

Phosphate glass fibers are an attractive alternative to silica fibers because they can be co-doped with much higher concentrations of Yb and Er and exhibit a higher optical gain per unit length. However, in such fibers the absorption of the pump is high and heating effects caused by the pump laser can cause a significant change in refractive index. This problem is overcome with a phosphate glass composition that exhibits a temperature coefficient of refractive index beta=dn/dT close to zero. This is achieved by avoiding alkali metal oxides in the glass composition and by adjusting the concentration of the network modifiers such as BaO.