Design and fabrication of LMA low-bending loss leakage channel fibers

We report design and fabrication of both all-glass fluorine doped and air-clad leakage-channel fibers (LCF) to achieve large-mode-area (LMA) and effectively single-mode operation with a minimum bending loss (BL) for compact Yb-doped fiber laser delivery applications. The BL and effective area for the fabricated LCF were numerically calculated by using full-vector FEM for both A-A' plane and B-B' plane. A high enough differential BL between the fundamental mode (~ 0.1dB/m) and the higher order mode (100dB/m) can be found in A-A' plane. The measured BL of the air-clad LCF was 0.09 dB/m and effective area of 350 μm² for 5 cm bending radius which is the best performance for minimum bendable LCF. The dispersion characteristic of the air-clad LCF is calculated and it has zero dispersion at 1.264μm. Single-mode nature of 1064nm light was measured at bent LCF. All-glass F-doped LCF was fabricated for easy splicing with standard SMF.