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.

中文翻译：

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二维六角结构光子晶体平板透镜的成像研究

基于时域有限差分法和平面波方法，研究了二维六边形结构光子晶体平板透镜的成像性能。首先，使用平面波扩展方法来验证结构具有负折射效果。当归一化频率为0.251时，等效折射率为– 1。时域有限差分法用于研究小圆形目标（半径为1/12波长）的结构的成像性能。仿真结果表明，具有六边形结构的光子晶体平板透镜可以大大提高目标的成像分辨率。然后改变方形气孔的边长，以研究对成像性能的影响。我们发现对于不同的边长，成像分辨率是不同的。a至0.5 a）。边长为0.5 a时，存在最佳分辨率。结果表明，可以通过改变孔的侧面长度来优化透镜的成像性能。它为光子晶体平板透镜的实际应用提供了理论依据。