Improving the mode profile circularity of microstructured optical fibers by using an Archimedean-like cladding structure

Abstract

We present a novel microstructured optical fiber (MOF) structure which consists of a 7-missing-holes core surrounded by a cladding formed by an Archimedean-like lattice of air holes, as opposed to the standard MOF cladding structure consisting of a triangular lattice. We demonstrate that this new cladding geometry can be achieved through the standard stack-and-draw MOF fabrication method, the main difference being the fact that the circular capillaries commonly used in conventional MOF are replaced by hexagonal canes comprising 7 air holes disposed in a centred hexagon (forming the so-called A7 unit cells). The Archimedean-like lattice MOF (ALMOF) is particularly interesting by the fact that it features a dodecagonal core, which is a shape much closer to a perfect circle than the hexagonally-shaped core characteristic of the conventional 7-missing-holes triangular-lattice MOF. As a result, we show that the improved core circularity of the ALMOF design leads to a significantly more circular fundamental mode profile, which can prove to be quite interesting for specific applications where the circularity of the mode profile is critical, such as precision laser micromachining for example.