基于半导体激光短阵列的976 nm高功率光纤耦合模块

摘要

By taking twelve 976 nm diode laser short bars as emitting units, a high power fiber coupled diode laser module with several hundred watts was developed. Firstly, the laser beam emitting from each diode laser short bar was shaped by a Beam Transform System (BTS) and a cylindrical lens, by which fast and slow axis beam parameter products could be symmetrized and the divergence was similar in the two directions. Then, every six diode laser short bars made up a laser stack by spatial multiplexing technology in the perpendicular direction and the laser beams from the two laser stacks were combined by polarization multiplexing. Finally, optimized triplet lens focused laser beams into a singlernmultimode fiber. Experimental results indicate that the continues wave optical power of the coupled diode laser module can reach to 418 W from the multimode fiber with a core diameter of 400 μm and numerical aperture of 0. 22,and its brightness is 2. 19 MW/(cm2 · sr). Matlab software was also applied to research of the near field intensity distribution of the laser spot output from the fiber and the result shows that the intensity distribution is a top hat, which proves that the module can be used in numerous applications like the welding and hardening of metal. The optical spectrum was also measured to determine the heat dissipation of the device and the result shows that the center wavelength of the device has shifted 6. 8 nm with the driving current increasing from 20 A to 50 A, and the spectral width is just 4. 12 nm (Full Width at Half Maximum,FWHM) for the diode laser short bar at the current of 50 A, which indicates that the device is favorable to the heat dissipation and could reliably work for long time. As compared with other candidates, the designed module has higher conversion efficiency and fiber output powers, and is suitable for the fields of material process and laser pumping.%采用12只出射波长为976 nm的传导冷却半导体激光短阵列为发光单元,研制出了百瓦级高功率光纤耦合模块.首先,利用光束转换器(BTS)和柱透镜对每只半导体激光短阵列进行光束整形,使得快慢轴方向光束质量接近并且发散角相同；然后,应用空间合束技术将每6只半导体激光短阵列在垂直方向上叠加,形成一个激光组,并利用偏振分束器(PBS)将两个激光组偏振合束；最后利用优化设计的三片式聚焦镜将激光耦合到光纤中.实验结果表明:该光纤模块的连续输出激光功率可达418.9 W,光纤芯径仅为400 μm,数值孔径(NA)为0.22,由此可得到激光亮度为2.19 MW/(cm2·str).利用Matlab软件分析光纤出射的光束形貌为平顶分布,显示其适合用于金属材料的硬化和焊接等领域.最后测量了模块的光谱,电流从20 A增加到50 A时,激光的峰值波长漂移了6.8 nm,并且在50 A时光谱宽度为4.12nm,表明该光纤耦合模块散热良好.同其它类型激光器相比,本激光模块电光转换效率和出光功率高,适用于材料加工和泵浦光纤激光器等领域.