Microstructured cladding elements to enhance the performance of large mode area leakage channel fibers

Large mode area fibers are imperative for scaling up the peak and average power of fiber lasers. Single-mode behavior and low FM loss are the crucial functionalities for these fibers. While rod-type Photonic Crystal Fibers (PCFs) have been very successful in offering large mode areas, the typical device length requirement (~1m) and rigid configuration limits their attractiveness for practical applications. LMA fibers offering a degree of bend tolerance are thus highly desired. Leakage channel fibers (LCFs) have shown a great potential for offering substantial bend tolerance along with large mode areas. However, the proposed use of Fluorine-doped rods in the all-solid version limits their practical design space. Here, we propose a novel design concept to attain single-material, large mode area fibers (mode area >~1000μm2) with effectively single mode operation coupled with bending characteristics comparable to all-solid LCFs and, at the same time, greater design flexibility and easier splicing relative to rod-type PCFs.