Microstructured optical fiber having large aperture core and smoothed fundamental mode, method of manufacturing the same, and its use in laser micromachining

摘要

The fiber comprises a core (2) having an index N and diameter of 10 μm or more, surrounded by a ring (4) having an index N+&Dgr;n and thickness &Dgr;R, and cladding (6) surrounding the ring and comprising for example air gaps (8). According to the invention: &Dgr;n≧10−3 and &Dgr;R=α/(&Dgr;n)&bgr; [1] where: 5×10−4 μm≦̸α≦̸5×10−2 μm and 0.5≦̸&bgr;≦̸1.5. The numbers α and &bgr; are dependent on the wavelength λ of the light guided by the fiber, the number of missing gaps therein, the diameter d of the gaps, the spacing Λ thereof and N. To design the fiber, λ, the number of missing gaps, d/Λ, the core doping content, Λ and &Dgr;n are chosen; and &Dgr;R is determined using equation [1] so as to obtain a flattened fundamental mode.