Selecting a high-power fiber-optic laser beam delivery system

Multimode optical fibers enable efficient flexible laser beam delivery but at a loss in the quality of the delivered beam. The fiber-optic beam delivery system effectiveness is strengthened by the optimal selection of its components not only for minimizing beam quality degradation but also for robustness. Smaller fibers tend to produce less degradation to beam quality but the minimum usable fiber size is limited by the quality of the laser beam, focusing optic and the numerical aperture of the fiber. Selection of the appropriate fiber type is an important consideration because the characteristics of the output beam enhance or degrade the utility of the fiber-optic-delivered beam for different applications. The other components of the beam delivery system also impact performance. High-power handling requires high-quality fiber end-face finish and special connectors that can withstand back-reflections. Recent developments in optical materials allow the manufacture of very low aberration optics that are particularly useful for short focal length lenses in output optics. Harnessing the Power of a high-power laser requires that knowledgeable and prudent choices be made when selecting the laser and its beam delivery system, We will focus on issues relevant to understanding and specifying a fiber-optic beam delivery system and provide some guidelines for specifying a system. Data obtained with high power Nd:YAG lasers will be used as illustrative examples.