中文说明：用matlab计算二维光子晶体带隙并做出带隙图 以及计算二维声子晶体（XY模）的能隙并作出图
English Description：
Matlab is used to calculate the band gap of two-dimensional photonic crystal and draw the band gap diagram. The energy gap of two-dimensional phononic crystal (XY mode) is calculated and plotted