Equal-frequency surface analysis of two-dimensional photonic crystals

This paper presents an analytical treatment of equal-frequency surface analysis of a two-dimensional photonic crystal. We first define the equal-frequency surface in terms of plane waves, which can be numerically evaluated. Then one- and two-plane-wave approximations are proposed, which consequently lead to analytical expressions of the equal-frequency surface. The approach presented is well suited to two-dimensional photonic crystals of weak dielectric modulation. For photonic crystals with a large modulation, the approach can be used to gain a general idea of the shape of the bands.