SBIR Phase II: Phase Locking of High Power Fiber Laser Arrays

这个小型企业创新研究（SBIR）二期项目旨在通过多核锁相光纤激光阵列实现有史以来第一个350W （cw）输出功率的高亮度和衍射限制激光束。在第一阶段，独特的功率组合概念的可行性已经通过锁相一组7掺镱单模光纤激光器，嵌入在一个共同的包层。此外，还建立了一个理论模型，对多芯光纤激光器阵列锁相的物理机制有了更深入的了解。这些结果清楚地表明，这一极具挑战性的第二阶段目标是可以实现的。然而，在开始商业化之前，仍有几个障碍需要消除。首先，必须对激光性能进行重大改进。这可以通过探索各种参数来实现，包括光纤长度、空腔精细度、增益饱和度、温度和应力分布，以及光纤结构参数，如纤芯分离和v值。此外，为了将泵的功率有效地耦合到包层中，必须进行数量级的改进。为了推进这一技术，将探索各种泵浦技术，特别是从包层壁侧面泵浦光纤激光器，而不是从光纤端面。如果研制成功，这将是在不造成灾难性破坏的情况下获得最大输出功率的最可行方法。最后，在非常高的功率水平下，必须通过提高功率损坏阈值来建立器件的可靠性。与高功率二极管泵浦固态激光器和二氧化碳激光器相比，高功率二极管泵浦多芯光纤激光器在市场上非常有竞争力，目前汽车、航空航天和造船行业用于金属和复合材料的精密钻孔、高速切割和焊接。

This Small Business Innovation Research (SBIR) Phase II project is aimed at achieving the first ever 350W (cw) output power in a high brightness and diffraction-limited laser beam from a multicore phase-locked fiber laser array. Under Phase I, the feasibility of the unique power combining concept has been demonstrated by phase-locking a group of 7 Yb-doped single mode fiber lasers, embedded in a common cladding. In addition, a theoretical model has been developed, providing a deeper understanding of physical mechanisms responsible for phase-locking of a multicore fiber laser array. These results clearly indicate that this extremely challenging goal for Phase II can be accomplished. Nevertheless, there remain several obstacles that need to be removed before embarking on commercialization. First, a significant improvement of the laserperformance must be made. This can be accomplished by exploring various parameters, which include fiber length, cavity finesse, gain saturation, temperature and stress distributions, as well as fiber structural parameters, such as core separation and the V-value. In addition, an order of magnitude improvement for efficient coupling of pump power into the clad must be made. To advance this technology, various pumping techniques will be explored, in particular the side-pumping of the fiber laser from the cladding walls, instead of the fiber end facets. If successfully developed, this could be the most viable way to obtain the maximum output power without causing catastrophic damage. Finally, the reliability of the device when operating at very high power level must be established by raising the power damaging threshold. High power diode-pumped multicore fiber lasers can be very competitive in the market place as compared to high power diode-pumped solid-state lasers and C02 lasers presently employed by automotive, aerospace and ship-building industries for precision drilling, high-speed cutting and welding of metals and composition materials.