Time independent rate equations for fiber laser are solved accurately with numerical method under multipoint boundary conditions. A novel method based on genetic algorithm is firstly proposed to optimize distributed pump powers and fiber segment lengths of kilowatt YDDC fiber laser. The uniformity of temperature distribution is improved by using optimized method. The calculated results show that the lower operating temperature and better uniformity can be obtained through increasing the number of segments at the cost of decreased output signal power.
A novel structure for efficient side-coupling of high power double-cladding fiber laser is presented. The maximum coupling efficiency of this structure is more than 90% for TM-polarization in +1 and -1 order but is only 40% for TE-polarization. Thus, a two-layer structure is introduced to obtain higher coupling efficiency for TE-polarization and maximum coupling efficiency almost 70% is demonstrated.