Combined effect of Yb inversion and pump photons on photodarkening in Yb laser fibers: experiments and model considerations

摘要

For constant Yb inversion and to increase pump power in the fiber core, a strong acceleration of the photodarkening (PD) process and a reduction in PD loss have been observed. The PD parameters determined by fitting the measured curves with the stretched exponential function are linked to the activation and deactivation rates of micro-optic centers (PD complexes). A phenomenological model is shown to reasonably describe the combined effect of Yb inversion and a direct influence of the pump power on these rates. It also offers the possibility of extrapolating the PD parameters to yield higher powers in the core of Yb fiber lasers. (C) 2019 Optical Society of America