研究了一种“光子晶体多层膜+波导层+光子晶体多层膜”对称薄膜的波导特性，光子晶体多层膜的第一禁带频率范围为73～99 THz。 采用多层介质平板波导理论研究了频率在73～99 THz间的电磁波在波导中的传输特性。结果表明波导传输的是TE0 和TM0 基模， 对于高次模式，不能在波导中传输，另外，频率在73～99 THz间的电磁波在波导层(中心层)的功率约束因子(Γ)在0.99～1之间， 即此时电磁波几乎完全局限在波导层内传输，为了比较，处在光子带隙外的频率分别为40 THz和50 THz的电磁波在波导层内的功率约束因子 分别为0.84和0.86，因此，利用光子带隙特征，由光子晶体多层膜构造的对称薄膜波导具有超低损耗特性。

A symmetry thin-film waveguide stacked by photonic crystals multilayer films was investigated, and its first stop band of photonic crystal multilayer film lies in the range of 73～99 THz. For the electric-magnetic wave with the frequency range of 73～99 THz, its transmission properties in the waveguide were investigated based on multilayer dielectric waveguide analysis method. The results show that only TE0 and TM0 modes can propagate in guided layer, furthermore, its power constrained factor in the guided layer (central layer) is in 0.99～1, in other words, the electromagnetic wave at 73～99 THz is fully constrained in guided layer, for comparison, the power constrained factor of electric-magnetic wave with the frequency of 40 THz and 50 THz out of stop band is 0.84 and 0.86, respectively. Thus, based on the stop band properties of photonic crystal, the symmetry thin-film waveguide stacked by photonic crystals multilayer films exhibits ultra-low attenuation property.