Abstract

Vector coupled-mode (VCM) theory, applied to helical Bloch waves [1], was recently introduced to clarify the origins of circular dichroism in twisted single-ring hollow-core photonic crystal fibres [2]. Here we show it can also be used to calculate, rapidly and precisely, the photonic band structure of regular lattices of coupled anisotropic waveguides, offering considerable advantages over the plane-wave expansion method and finite element modelling (FEM). As an example, we treat a graphene-like lattice of coupled cores (Fig. 1a), which represents the type of mode seen in coreless twisted PCF [3]. The VCM approach itself is illustrated in Fig. 1b.

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