SBIR Phase I: Manufacturing High-Density Defect-Free and Phase-Locked Fiber Laser Arrays

该小型企业创新研究（SBIR）第一阶段项目旨在制造高密度锁相光纤激光器阵列，该阵列可以以极高的精度和质量制造，不会产生机械缺陷。该公司开发了一种新颖的相干功率合成技术，将一组特殊结构的锁相光纤激光器组合在一个公共包层中，使它们的相位同步，有利于通过强倏逝波相互作用的基本同相模式。结果表明，锁相光纤激光器和放大器的输出可以在紧凑的封装中提供极高的功率（几千瓦）和良好的光束质量（M2 1.5）。这样的激光器是非常理想的材料加工和精密制造，并提供了许多有吸引力的特点，如可维护性，可运输性和负担得起的。公司开发了一种有效的侧面泵浦技术，通过这种技术，可以在远超过吸收长度的长光纤长度上建立均匀的增益。将无缺陷的多芯光纤与这种侧面泵浦技术相结合，将有可能在直径约50微米的光斑尺寸（相当于大于10 MW/cm 2的激光强度）中实际地将锁相光纤激光器阵列的输出功率缩放到多kW，而不会遇到灾难性故障。在第一阶段，工作重点将是设计和试验无缺陷的锁相光纤阵列。此外，将进行实验，以验证不仅与光纤芯面积而且与长度成比例的功率缩放定律。结果将用于制定第二阶段的原型。在商业上，由于光纤激光器的效率比固态激光器高至少4倍，并且工作在比CO2激光器更理想的波长下，因此它将有更好的机会在市场上成功取代现有的固态和CO2激光器，这些激光器已被广泛用作当今航空航天、汽车、造船、耐火金属、石墨和复合材料工业。通过这些技术进步，可以经济可靠地制造具有高亮度光束的多千瓦光纤激光器，并可以为精密制造提供数量级的速度和高分辨率。

This Small Business Innovation Research (SBIR) Phase I project is aimed for manufacturinghigh-density phase-locked fiber laser arrays that can be made with extremely high precision andquality that will be free from mechanically induced defects. The company has developed a noveltechnique for coherent power-combining a specially structured group of phase-locked fiber lasersin a common cladding so that their phases are synchronized in favor of the fundamental in-phasemode through strong evanescent wave interaction. It has been shown that the output of phase locked fiber lasers and amplifiers can provide extremely high power (multi-kW) with a goodbeam quality (M2 1.5) in a compact package. Such a laser is very desirable for materialprocessing and precision manufacturing and offers many attractive features, such asmaintainability, transportability, and affordability. The Company has developed an efficient side-pumping technique by which a uniform gain can be established over a long fiber length far exceeding the absorption length. Combining a defect-free multi-core fiber with this side pumping technique, it will be possible to realistically scale the output power of a phase-locked fiber laser array up to multi-kW in a spot size of about 50 micron in diameter (equivalent to a laser intensity greater than 10 MW/cm2) without encountering catastrophic failure. Under Phase I, efforts will be focused on designing and experimenting with a defect-free phase-locked fiber array. In addition, experiments will be performed to verify the power-scaling law that is proportional to not only the fiber core area but also the length. Results will be used to formulate the prototype for the Phase II. Commercially, because fiber laser efficiency is at least 4 times higher than the solid-state laser and operates at a more desirable wavelength than the CO2 laser, it will have a much better chance to succeed in the market place to replace the existing solid-state and CO2 lasers, which have been used extensively as precision machine tools for present-day manufacturing in aerospace, automotive, ship-building, refractory metals, graphite, and composite materials industries. With these technological advancements, a multi-kW fiber laser with a highbrightness beam can be manufactured economically and reliably and can offer an order of magnitude increase in speed and high-resolution for precision manufacturing.