Few-Mode Lensed Fibers

Few-mode lensed fiber for focusing multiple spatial modes with minimal distortion are proposed and investigated numerically and experimentally, for the first time to the best of the authors' knowledge. Although the conventional hyperbolic lens profile works effectively for the fundamental mode, it introduces severe distortion for high-order radial modes. This distortion is due to destructive interference between out-of-phase lobes in the radial direction. To reduce this distortion, we modify the lens profile to avoid such destructive interference. Focused images with significantly reduced distortions were observed in our experiments.