中文说明：
光子晶体的能带图计算，其实质就是电磁本征值（复矢量场）的问题。利用平面波展开磁场，引入f(r)=1/eps(r)，再利用倒格矢G将f(r)展开，将两者代入光子晶体的支配方程，最后得到一个平面波展开的方法的线性方程组，最终转化为求解其特征值向量的问题。
English Description：
The essence of photonic crystal band diagram calculation is the problem of electromagnetic eigenvalue (complex vector field). The magnetic field is expanded by plane wave, f (R) = 1 / EPS (R) is introduced, and then f (R) is expanded by inverse lattice vector g, which is substituted into the governing equation of photonic crystal. Finally, a linear equation system of plane wave expansion method is obtained, which is transformed into the problem of solving its eigenvalue vector