A global design of high power Nd-Yb co-doped fiber lasers

A global optimization method - niche hybrid genetic algorithm (NHGA) based on fitness sharing and elite replacement is applied to optimize Nd³⁺-Yb³⁺ co-doped fiber lasers (NYDFLs) for obtaining maximum signal output power. With a objective function and different pumping powers, five critical parameters (the fiber length, L; the proportion of pump power for pumping Nd³⁺, η; Nd³⁺ and Yb³⁺ concentrations, N_Nd and N_Yb and output mirror reflectivity, R_out) of the given NYDFLs are optimized by solving the rate and power propagation equations. Results show that dividing equally the input pump power among 808 nm (Nd³⁺) and 940 nm (Yb³⁺) is not an optimal choice and the pump power of Nd³⁺ ions should be kept around 10-13.78% of the total pump power. Three optimal schemes are obtained by NHGA and the highest slope efficiency of the laser is able to reach 80.1%.