中文说明：资源描述从一维光子晶体的能带结构（图不难看出，在垂直入射时，即 时，偏振及偏振的能带重合。实际上这是由于一维结构对于入射光轴具 有旋转对称性导致的简并。而对于离轴传播（来说，旋转对称性不再满 足，偏振及偏振的能带不再重合。此外离轴及轴上的能带结构最大的不 同之处在于：当取所有可能的时，带隙消失。一般来说，对于多层膜结构的 光子晶体，这种情况是普遍存在的。原因是：对于为无穷大的波矢来说，介 电常数在空间分布的周期性消失，进而导致带隙消失。
English Description：
Application backgroundIt is not difficult to see from one dimensional photonic crystals with a structure (Fig.When the polarization and the polarization of the band overlap. In fact, this is due to the one-dimensional structure of the incident optical axisDegenerate with a rotational symmetry. But for the propagation of the off-axis (the rotational symmetry is no longer fullThe energy band of the foot, the polarization and the polarization can no longer coincide. In addition to the energy band structure of the shaft and shaftThe same is: when all the possible, the band gap disappears. In general, for a multilayer structurePhotonic crystals, such a situation is ubiquitous. The reason is that: for the infinite wave vector, theThe periodic disappearance of the electric constant in the space distribution, which leads to the disappearance of the band gaps.