Imaging of photonic crystal slabs with non-ideal effective refractive index

摘要

Finite-sized photonic crystal slabs have an effective refractive index that differs from that calculated for infinite structures. We investigate the imaging characteristics of such slabs with non-ideal effective refractive index n_(eff), namely | n_(eff)<1 and [ n_(eff) | >1 at the 2~(nd) band of hexagonal lattice, and observe an approximately linear object-image relation and saturated imaging. We focus on the slab aperture effect on imaging and analyze the mechanisms of image formation. For the finite-sized photonic crystal slab with fixed object distance, due to beam leakage, there is a limiting aperture size beyond which the image resolution and image distance remain almost unchanged. A larger aperture does not necessarily lead to higher image resolution. In order to be focused by the slab with negative refraction, the physical source or the object must contain sufficient transversal wavevectors or higher transversal spatial frequencies. The analyses are for the cases where propagating waves dominate imaging formation.