Experimental study of high power photonic crystal fiber laser

The influences of the pump absorption coefficient on the temperature distribution along the fiber are analyzed for fiber lasers in theory based on the thermal conduction equations. It is shown that the temperature of the fiber with low absorption coefficient is comparatively low and the temperature distribution is very smooth, so the thermal damage can be effectively avoided. According to the analysis, an Yb-doped photonic crystal fiber with the pump absorption coefficient of 1.45 dB/m is used for the fiber laser in the experiment. 428.5 W single-mode continuous-wave output power is achieved at the pump power of 560 W. The slope efficiency of the system is 76.5% and the beam quality factor M2<1.2. The temperature of the fiber is measured at 25 cm from the fiber ends which are cooled with c