填充率渐变引起的能带结构和等频面结构的变化是填充率渐变型波状结构二维(2D)光子晶体(PC)产生光路转弯现象的根本原因,由于TM模和TE模在能带结构上存在差异,光路转弯现象就具有明显的偏振选择特性,能够实现归一化频率a/λ为0.29～0.33的偏振分束。利用时域有限差分(FDTD)法模拟了TM模的U型转弯波导,发现出射光位置对入射波长和入射角的变化很敏感,位移变化量分别达到0.38 μm/10 nm和0.29 μm/(°)。利用TM模的U型转弯波导构建了新型的平行平面谐振腔,并指出由填充率渐变型波状结构二维光子晶体和一维多层薄膜构成的混合结构在光分束和抑制光束发散方面的作用及其在平行平面谐振腔中的潜在应用。

The light-path bending phenomenon in filling-factor graded wavelike two-dimensional (2D) photonic crystals (PC) is due to the gradual modifications of the band structure and iso-frequency surface. Because of the band structure difference between TM and TE mode, the light-path bending phenomenon is polarization dependent, which is suitable for the polarization splitter in the normalized frequency a/λ region from 0.29～0.33. In the U-shaped bending waveguide of TM mode, the position of the emergent light is very sensitive to the incident wavelength and incident angle. The simulations with finite-difference time-domain (FDTD) method show that the sensitivities are 0.38 μm/10 nm and 0.29 μm/(°), respectively. The plane-parallel resonant cavity is built up in theory with the U-shaped bending waveguide for TM mode. The beam splitting and convergence effect are also discussed for the structure composed of filling-factor graded wave-like 2D-PC and one-dimensional multilayer thin films. This kind structure has the potential application in the plane-parallel resonant cavity.