Imaging Research of Two-Dimensional Photonic-Crystal Flat Lens with Hexagonal Structure

Abstract

Based on the finite-difference-time-domain method and the plane-wave method, we study the imaging performance of two-dimensional hexagonal-structure photonic-crystal flat panel lens. First, the plane wave expansion method is used to verify that the structure has a negative refraction effect. The equivalent refractive index is – 1 when the normalized frequency is 0.251. The finite-difference-timedomain method is used to study the imaging performance of the structure for the small circular target (radius 1/12 wavelength). The simulation result shows that the imaging resolution of the target is greatly improved by a photonic-crystal flat lens with hexagonal structure. Then the side length of square air hole is changed to study the influence on the imaging performance. We find that the imaging resolution is different for different side lengths. The general trend is that the imaging resolution gradually increases, when the side length of hole increases (from 0.1 a to 0.5 a). There is an optimum resolution when the side length is 0.5 a. The result shows that the imaging performance of the lens can be optimized by changing the side length of holes. It provides a theoretical basis for the practical application of the photonic-crystal flat lens.