Application of finite element methods to photonic crystal modelling

Photonic crystals (PCs) are materials with a periodically modulated dielectric constant, through which certain frequencies of electromagnetic radiation cannot propagate. The modes admitted by PCs can be investigated effectively using the finite element method with the assistance of the Floquet-Bloch theorem, by considering a unit cell of the material and imposing periodic boundary conditions. Along with the Dirichlet and metric matrices, a third type of elemental matrix emerges. The types of results that are of interest to photonic crystal manufacturers are introduced and presented; in this context, the benefits of using the subspace iteration method to solve the eigensystems are discussed. The performance of the algorithm is investigated with respect to mesh granularity and interpolation order.