Imaging properties of an elliptical-rod photonic-crystal slab lens

Abstract

Imaging properties of a photonic-crystal (PC) slab lens consisting of a square lattice of elliptical dielectric rods in air are studied theoretically. The finite-difference time-domain technique is used to investigate the field patterns of a TM-polarized point source placed in the vicinity of the PC slab. A good-quality image can form in the opposite side of the slab in a frequency window located slightly below the fundamental band gap, but it is strongly confined in the near-field region irrespective of change of the slab thickness. We have changed the orientation of the elliptical rods with respect to the surface normal of the slab, and found that when the major or minor axis of the rods is not collinear with the surface normal, the image spot can show a vertical shift away from the horizontal line passing the point source. The simulation results are consistent with the equifrequency-surface contour analysis for these elliptical-rod photonic-crystal structures.