利用平面波展开法计算二维光子晶体柱子带隙结构。参考文献中国知网文章：用平面波展开方法计算二维光子晶体带隙结构。-Using the plan wave expresion calculate two-dimension photonic crystals band gaps structure, reference:Calculating the photonic band gap structure of two-dimensional photonic crystal using the p