High Average Power Fiber Laser Technology

At present, fiber lasers have become one of the hotspots in the solid-state lasers fields, which have widespread applications in the fields of communications, sensor, spaceflight, life sciences and industry because of low threshold, high efficiency, all solid-state and compactness.The designs of coupling system and fiber parameters were analyzed, which are the most important technique for high average power fiber lasers. The aberration-free fiber coupling lens pair has been presented, which is made of two non-spherical lenses with a focused length of 11mm and 4.5mm, numerical aperture of 0.25 and 0.45, respectively. The simulative coupling efficiency was higher than 80% in the case of coupling 600um, NA 0.22 beam into diameter 400um, NA 0.46 fiber. The inner clad breaking symmetry of ray propagation can enhance the absorption efficiency of the pump light. Numerical analysis of dependence of output power on pump power, fiber length, doped concentration, mirror reflectivity and loss has been carried out, which provides foundation for fiber lasers design.On the basis of the theoretical analysis, the fiber laser experiment has been performed in the case of two-end open cavity. When incident pump power was 9.32W, the output power of 3.16W was attained with coupling efficiency of 80.7% and slope efficiency 35.7%. The experimental data are in agreement with numerical analysis results, as thus the theoretical model is proved to be correct.