Large-Mode-Area All-Solid Photonic Bandgap Fibers for the Mitigation of Optical Nonlinearities

There is still significant need for power scaling of fiber lasers. Large-mode-area fibers are a key for the mitigation of optical nonlinearities. In recent years, mode instability has shown itself to be an additional significant limiting factor for single-mode power scaling in the regime of a few hundred watts to kilowatts. It is better appreciated now that further power scaling requires significant high-order-mode suppression in addition to a large effective mode area in a fiber. In recent years, we have shown that all-solid photonic bandgap fibers are a superior approach due to their unsurpassed higher-order-mode suppression in large-mode-area designs, making them well suited for applications at high average powers. We will review of some of the recent progress, challenges, and prospects of all-solid photonic bandgap fibers in this invited paper.

I. Introduction

Fiber Lasers have been a revolutionary force in manufacturing in the past decade. It is well known now that high-power lasers can be used to machine a wide range of materials from plastics to glass and ceramics. Their non-contact nature makes them very low maintenance and cost-effective. An optical beam can be repositioned more rapidly than any mechanical tool, making it ideal for mass production. The machining precision with a diffraction-limited spot size is also significantly better than any conventional machining techniques. It was only a little over a decade ago when laser-based machining started to revolutionize industrial manufacturing due to the development of highly reliable fiber lasers with high average powers. The commercial fiber laser market has been growing at double-digit rates for the past decade. Further power scaling is critical to increase capabilities and throughput in manufacturing.