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The photonic crystal fiber (PCF) is a micro-structured fiber, where arrays of holes running along the waveguide length, has more controllable fabrication parameters than a standard single mode fiber. Increasing interest is being shown in such PCFs for a range of applications in optical communications, sensing and signal processing. This includes the control and guidance of optical beams, taking advantage of their unique transmission characteristics, including being continuously single-moded, with controllable spot-sizes and with tailored group velocity dispersion characteristics. To date, most of the research into these fibers has a strong experimental basis [1], which has recently been complemented by various modal solution approaches to their characterization, but mostly using scalar formulations or being limited to specific types of structures. The modal solution approach based on the powerful finite-element method (FEM) [2] is more flexible, can represent any arbitrary cross-section more accurately and has been widely used to find the modal solutions of a wide range of optical waveguides [2]. The optical modes in a high-index contrast PCF with two-dimensional optical confinement are also hybrid in nature. To accurately characterize such fibers a full-vectorial approach is necessary and a H-field based full vectorial approach [2] has recently been extended to study the polarization issues in such PCFs. Polarization dependent single mode operation, variation in the spot-size, modal field profiles, modal hybridism, birefringence, and the beat length have been calculated for these fibers. REFERENCES [1] J C Knight et al., Opt. Lett., 21, pp.1547-1549, 1997. [2] B M A Rahman and J B Davies, J. Lightwave Tech., 2, pp.682-688, 1984. |
