Research on beam collimation of high power laser diode array

近年来随着大功率半导体激光器制造工艺的成熟和生产成本的降低，其应用范围越来越广泛。但是固有的结构特点也造成了其光束发散角较大，存在固有像散的缺点，这给实际应用带来了很大的麻烦。一个很好的解决办法就是把光束耦合进光纤中，不仅实现柔性传输，增加使用的灵活性，而且可以直接应用于本身就需要光纤的场合。 近几年发展起来的一种耦合方案是整形耦合法，其包括光束准直、光束整形、光束聚焦三部分。本课题主要对大功率半导体激光器阵列光束准直技术进行了研究。 本论文调研了国内外发展趋势，比较了不同的光束准直技术，相对于其它的准直方式，利用光纤柱透镜实现快轴光束准直、自聚焦光纤透镜实现慢轴光束准直的方法具有准直效果好，成本低等优点。 利用光纤柱透镜对半导体激光器阵列光束快轴进行准直可以实现出射光线发散角在5mrad以内，透过率高达95％，并与现在商用的利用平凸柱透镜对快轴光束准直进行了详细的比较分析。 对自聚焦光纤透镜的原理进行了分析，综合考虑到自聚焦光纤透镜的焦距和端面研磨的方便，确定了实验中自聚焦光纤透镜的长度。利用Zemax进行序列光线追迹和参数优化，分析了自聚焦光纤透镜的像差特性，并与相同尺寸商用的微柱透镜进行了比较，发现两者的像差特性相差不大。 利用自聚焦光纤透镜实现大功率半导体激光器阵列光束慢轴方向的准直，需要使每一根自聚焦光纤对准一个发光单元。实验中，制作了具有周期结构的V型槽，确保自聚焦光纤透镜之间的间隔。制作了半导体激光器阵列准直系统，并实现了大功率半导体激光器阵列光束的准直。 论文的最后利用几何光学方法和重叠积分的方法分析了激光光束到多模光纤耦合效率的问题。In recent years, laser diodes are widely used in various regions, because fabrication of high power laser diode is grown up and the cost of production is reduced. The output radiation from laser diode is highly divergent and astigmatic, because of its existing configuration, which has restricted its applications. Coupling laser beam to fiber is a good method for its using. In fiber, it can deliver freely and can be used in some fields using fibers directly. How to couple laser beam to fiber efficiently is a key technique. In recent years, beam-shaping methods are rapidly developed which include beam collimating, beam-shaping and beam focusing. This article chiefly studies the beam collimating of high power diode arrays laser. This article researches the internal and oversea development, and compares the different collimating techniques. Compared with other techniques, the method of beam collimation through the fiber micro-lens in fast axis direction and through the GRIN optical fiber in slow-axis direction, has good collimation and low cost. The divergence angle in fast axis direction of high power diode arrays laser can be collimated within 5 mrad through the fiber lens, and up to 95% power can get across. The results are detailedly compared with those of commercial application using aspherical cylindrical lens. We have analyzed the theory of GRIN fiber lens, and decided the length of the GRIN fiber lens, considering the focal length and convenient polishing. Compared with the equivalent cylindrical micro-lens, we analyzed the characters of ray aberration obtained by sequential components ray tracing of optical design software ZEMAX, and optimized the parameters. The both results are almost the same. Collimating high power diode laser in slow-axis direction through GRIN fiber lens, every GRIN fiber lens need aimed at the emitters of laser diode array. We fabricated the V-type grooves with 500um spacing, and collimated the high power diode laser. Finally, we analyzed the coupling efficiency of laser beam to multimode fiber, using geometrical optics approach and overlapping integral theory respectively