Measurement of photodarkening resistance in heavily Yb3+-doped silica and silicate fibers

We report the measurements of photodarkening in single-mode heavily Yb
³⁺
doped silica and silicate fibers. Our data shows that under strong pumping conditions, the silicate fiber allows 13 times greater Yb
³⁺
concentrations than the most photodarkening-resistant silica fibers to date without the onset of photodarkening at 635 nm.