Fabrication of Micro Fresnel Zone Plate Lens on a Mode-Expanded Hybrid Optical Fiber Using a Femtosecond Laser Ablation System

We present a compact all-fiber zone plate lens directly ablated on the surface of a mode-expanded hybrid fiber end by using a high precision femtosecond laser processing technique. To achieve a sufficiently large beam size and focusing efficiency, a segment of a coreless silica fiber having a 200-mu m diameter was adapted. Focusing properties of the zone plate lens were experimentally investigated and compared with numerical simulations.