Influence of Fibre Bending on the Laser Modes of a Large Mode Area (LMA) Multimode Er3+/Yb3+ co-doped Fibre Laser
Z-F. Deng, S-B. Zhan, Y. Wang, W-R. Le and F. Tang
For the large mode area (LMA) multi-mode Er3+/Yb3+ co-doped double-clad fibre laser, an experimental system about the influence of the fibre bending diameter on the laser modes has been designed and established. The radio of power of different modes in multimode laser with different bending diameters was analysed theoretically, revealing that the low-order modes have higher power than the high-order modes under the same fibre bending diameter. The experimental results show that when the bending diameter was 400, 150 and 65 mm the laser beam quality factor (Mx2) was 3.92, 3.51 and 2.72 with the number of longitudinal modes of 5, 4 and 2, respectively. Further, the experiment demonstrated the correspondence between bending diameter and the laser modes, which is that the bending fibre can reduce the number of laser modes, indicating that the laser beam near the diffraction limit can be obtained by this method.
Keywords: Fibre laser, Er3+/Yb3+ co-doped, large mode area (LMA), curved fibre, output performance, curvature losses, laser modes