Focusing Properties of Graded Index Photonic Crystal Structures Made of Material with Different Refractive Index

In this paper we investigate focusing properties of graded photonic crystal structures with different refractive indices. Graded structure is composed of air holes in dielectric background. The holes radii are varied in direction transverse to propagation. While increasing refractive index of background of graded structure, the effective refractive index of the structure increases. With increasing effective refractive index, the focusing power of the graded structure increase and outgoing wave at focal point will be more focused. The Finite-Difference Time-Domain method was employed to compute field propagation through the structure..