MICROSTRUCTURED POLYMER OPTICAL FIBRES -the exploration of a new class of fibres- Martijn A van Eijkelenborg (1), Alexander Argyros (1,2), Geoff Barton (3), Ian Bassett (1), Felicity Cox (1,2), Matthew Fellew (1,2), Simon Fleming (1), Geoffrey Henry (1), Nader Issa (1,2), Maryanne Large (1), Steven Manos (1,2), Whayne Padden(1), Leon Poladian (1), Joseph Zagari (1,3) 1 : Optical Fibre Technology Centre, Australian Photonics Cooperative Research Centre, University of Sydney, 206 National Innovation Centre, Australian Technology Park, Eveleigh NSW 1430, Sydney, Australia Email:M.Eijkelenborg@oftc.usyd.edu.au 2 : School of Physics, University of Sydney, Sydney, NSW 2006, Australia 3 : Department of Chemical Engineering, The University of Sydney, NSW 2006 Australia Abstract: Progress on microstructured polymer optical fibres (MPOFs), a new class of polymer fibres that were developed last year, will be presented, including various single-mode MPOFs, highly birefringent MPOF, twin-core MPOF, nonlinear MPOF, graded-index MPOF and hollow core MPOF, the latter case being where light is guided in an air core. © 2002 ICPOF 1. Introduction A new class of polymer optical fibres was reported last year [1-5], in which the guiding of light is achieved by the introduction of a pattern of microscopic air holes that run down the entire length of the fibre. These microstructured polymer optical fibres (MPOFs) offer many new opportunities and can significantly enhance the functionality of POFs. The idea to guide light using microstructure has been explored in silica fibres, in so called photonic crystal fibre (PCF), microstructured fibre (MOF) or holey fibre (HF) [6,7]. It has been shown that single- mode guidance in a relatively large core (20 μm diameter) [6] is possible, as well as guidance in an air core. MPOF allows many advantages over their glass counterpart. Firstly, fabrication is much easier due to the much more favourable balance between surface tension and viscosity at the draw temperature which reduces the chance of holes collapsing. Secondly, the microstructure is not restricted to close-packed arrangements of circular holes, as is the case for glass. Thirdly, more material modifications are possible, owing to the much lower processing temperatures and the intrinsic tailorability of polymers. This offers the potential of fabricating fibre with specific functionality not otherwise obtainable. The combination of low-cost fibre fabrication and large-spot single-mode or multi-mode guidance provides potential advantages for MPOF in applications such as local-area networks (LANs). In addition, polymers with higher glass transition temperatures can be used for MPOF, offering advantages for high temperature applications e.g. in the automotive industry. A large range of different fibres can be fabricated within the same fabrication framework. Simple changes in the microstructure can provide fibres with distinctly different functionalities. In this paper, we present an overview of recent MPOF work, including examples and results of single-mode MPOF, highly- birefringent MPOF, electro-optic MPOF, twin-core MPOF, Graded-Index MPOF, ring-structured MPOF, and hollow-core MPOF, in which light can be guided in an air core. Fig. 1 Example of a fabricated single-mode microstructured polymer optical fibre (MPOF) with air holes spaced at 3.5 μm. 2. Fabriction and materials A range of different materials and fabrication methods can be used to make MPOF preforms. In addition to the capillary stacking technique traditionally used for glass PCF, polymer preforms can be made using techniques such as extrusion, polymer casting, polymerization in a mould or injection moulding. With such techniques available, it becomes straightforward to obtain different cross-sections in the preform, with holes of arbitrary shapes and sizes in any desired arrangement (see Section 4). This is a major advantage over silica-glass based PCF, where the hole structure is mostly restricted to hexagonal or square close-packed structures due to the capillary stacking technique used. Invited talk at the Asia-Pacific Polymer Optical Fibre Workshop, 3-4 Jan 2003, Hong Kong, China