Optical Tamm states in photonic structures made of inhomogeneous material

We demonstrate a tunable optical Tamm state at the interface between a photonic crystal (PC) and a film with non-uniformly varying refractive index. The optical Tamm state is associated with a sharp transmission peak and strong localization of the electric field. It is spectrally located inside the overlapping band gaps. The shift of the optical Tamm state is sensitive to the lattice constant of the inhomogeneous material. Our results provide an approach to tailor interface states in a controllable manner.