Stable output and beam profile at high power laser operation is a prime requirement for precision high-end manufacturing. The stability of laser charateristics during power scaling in a single-oscillator is limited by several unavoidable non-linear effects. Hence, kW-level power scaling through multiple amplification stages or using signal combination are feasible solutions. In a master oscillator power amplifier (MOPA) architecture, pump-signal combiner with high pump coupling efficiency and low loss signal transmission maintaining seed beam quality during coupling from a single mode fiber into a large mode area fiber, is an important component. In this respect, an effective method of fabricating mode-field matched pump-signal combiner has been presented employing a section of intermediate fiber, having adiabatically tapered core and uniform cladding, along with a conventional signal fiber (termed hybrid signal fiber) inside the input fiber bundle to obtain effective mode-field matching of signal light in between the input fiber bundle and the output fiber. Additionally a taper-less signal combiner design has been proposed for scaling laser power through incoherent combination. The reduced-clad signal fiber with low loss core guidance supports bundling of the input fibers inside an economic low-OH silica tube to obtain good transmission efficiency and beam profile.

中文翻译：

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先进制造中高功率光纤激光器的模场匹配泵浦信号组合器


高功率激光运行时稳定的输出和光束轮廓是精密高端制造的首要要求。单振荡器功率缩放期间激光特性的稳定性受到几种不可避免的非线性效应的限制。因此，通过多个放大级或使用信号组合进行千瓦级功率缩放是可行的解决方案。在主振荡器功率放大器（MOPA）架构中，具有高泵浦耦合效率和低损耗信号传输的泵浦信号组合器是一个重要组件，在从单模光纤耦合到大模面积光纤期间保持种子光束质量。在这方面，提出了一种制造模场匹配泵浦信号组合器的有效方法，该方法采用一段具有绝热锥形纤芯和均匀包层的中间光纤，以及输入内部的传统信号光纤（称为混合信号光纤）。光纤束，以获得输入光纤束和输出光纤之间信号光的有效模场匹配。此外，还提出了一种无锥度信号组合器设计，用于通过不相干组合来缩放激光功率。具有低损耗纤芯引导的减少包层信号光纤支持将输入光纤捆绑在经济的低 OH 石英管内，以获得良好的传输效率和光束轮廓。