Numerical comparison of pumping methods for high-power Er/Yb-codoped fiber lasers

Abstract

The amplified spontaneous emission (ASE) in the Yb band and thermal damage are the main obstacles to the power scaling of high-power Er/Yb-codoped fiber lasers (EYDFLs) and amplifiers. In this paper, three popular pumping methods, i.e., off-peak pumping, core pumping with ytterbium-doped fiber laser, and cascade co-pumping, the conquering of these obstacles is investigated and compared based on numerical simulation. The influence of the pump wavelength is systematically analyzed. Performances, including thermal effects, optimal fiber length, and maximum applicable pump power and expectable output power are compared for EYDFLs with these pumping methods. The results show that off-peak pumping and core pumping can alleviate the Yb ASE problem and increase the achievable output power to some extent. We believe this improvement fundamentally originated from the lower absorption coefficient that alleviates the bottlenecking effect. The Yb ASE problem is still inevitable for these two methods, whereas the cascade co-pumping method can completely extricate a EYDFL from the restrict of this problem and push the power to the thermal damaged limitation.