Surface waves in finite one-dimensional photonic crystals: mode coupling

The coupling properties of surface waves in finite one-dimensional photonic crystals are analyzed. It is found that in a finite periodic system of alternating dielectric layers bounded by air, the surface modes of each boundary can interact and become coupled in a variable degree depending both on the truncation of the outer layers and the total thickness of the crystal slab. The truncation of outer layers determine the position of the modes inside the band gaps and consequently the magnitude of the decaying length (of electric field) which is minimum in the center and becomes infinite at the edge of band gaps. In this way, the total thickness of the crystal slab must be correlated to the decaying length in order to control the strength of interaction between modes.