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。-Energy band diagram of the photonic crystal, its essence is the electromagnetic eigenvalues ​ ​ (complex vector field).The linear plane wave expansion magnetic field, the introduction of f (r) = 1/eps (r), re-use reciprocal lattice vector G will expand f (r), the two substituted into the governing equations of the photonic crystal, and finally get a plane wave expansionequations, and ultimately into solving the problem of its eigenvalues​ ​ .