Band gap transformation in three-component 2D photonic crystals

Abstract

In this paper we analyze theoretically how introduction of the third component into the two-dimensional photonic crystal influences on the photonic band structure and the density of states of the system. We consider the periodic array of cylindrical air rods in a dielectric and the third medium is introduced as an intermediate layer of the thickness d and the dielectric constant ei between the air pores and the dielectric background. Various combinations of the parameters R (pores radius), d, and ei which allow the band gap to appear were considered. Using the plane wave method we have obtained the band structures and density of states for the triangular lattice 2D photonic crystals. The dependencies of the band gaps width and gaps edges position on the interlayer dielectric constant and interlayer thickness were analyzed. In the framework of this approach we have estimated the influence of the surface oxide layer on the band structure of macroporous silicon. We observed the shift of the gap edges to the higher or lower frequencies depending on the interlayer thickness and dielectric constant. We have shown that the existence of a native oxide surface layer should be taken into consideration to understand the optical properties of 2D photonic crystals, particularly in macroporous silicon structures.