High-power fiber laser materials: influence of fabrication methods and codopants on optical properties

In this contribution the influence of fabrication technique (solution doping, gas-phase doping) and the choice of suitable material systems (Al, P, Yb:SiO2 and Al, F, Yb:SiO2) for high power fiber laser materials on their optical properties is analyzed. The materials under analysis contain low amounts of codopants (Yb < 0.15 mol%, other <1.2 mol%). The effects on refractive index, attenuation, absorption and emission cross section as well as on photodarkening are addressed. The main part concerns with the analysis of photodarkening, in fact the evolution of individual defect centers are spectrally and temporally investigated by means of 2D curve fitting. It is suggested that this spectro-temporal fitting procedure can lead to new insights in the development of photodarkening on a level of the defects themselves.