中文说明：
二维光子晶体禁带的MATLAB源码,光子晶体中因周期性结构而存在的频率禁带称为光子禁带，光子禁带的存在是光子晶体具有广泛应用前景的重要原因。 禁带越大，可控光的频带也越宽
English Description：
Matlab source code of two-dimensional photonic crystal band gap. The frequency band gap in photonic crystal due to periodic structure is called photonic band gap. The existence of photonic band gap is an important reason for the wide application prospect of photonic crystal. The larger the band gap, the wider the frequency band of controllable light