Theoretical analysis of the influence of Photodarkening on the gain of a YDCFL

An analytical formulation was developed to study the influence of the Photodarkening (PD) on the gain behavior of a ytterbium doped double-clad fiber laser (YDCFL). To formalize the modeling, the fundamental equations that describe the continuous wave laser in the steady state tandem pumping regime were employed. It was possible to observe the dependence of the YDCFL signal gain with temperature, absorption and emission cross sections, and with the higher level population density. Since the gain is related to these laser parameters, it may change significantly with increasing temperature in the fiber due to the PD effect