设计了基于自准直效应的硅光子晶体TE模式1×3和1×2光下路分束器。1×3光下路分束器由4个分束镜组成，而1×2下路分束器由3个分束镜和1个反射镜组成。利用多光束干涉原理推导出光下路分束器各个出口的透射谱理论公式。通过选择合适的分束镜，可以得到不同分束比例的光下路分束器。对于1×3光下路分束器，设计了1∶1∶1和1∶2∶3两种分束比例；对于1×2光下路分束器，设计了1∶1和1∶2两种分束比例。再利用时域有限差分软件数值模拟了透射谱，其结果与理论设计一致。当下路波长为1550 nm时，1×3和1×2两种光下路分束器的大小均约为10 μm ×10 μm，自由光谱区为36 nm，覆盖了整个光通信C波段。

The paper reports 1×3 and 1×2 photonic drop splitters (PDSs) for TE modes in a silicon photonic crystal based on self-collimation effect. The 1×3 PDS consists of four beam splitters and the 1×2 PDS consists of three beam splitters and one mirror. The theoretical transmission spectra at different drop ports in PDSs were analyzed with the multiple-beam interference theory. The PDSs with different splitting ratios can be designed by selecting beam splitters appropriately. For the 1×3 photonic drop splitter, we designed two splitting ratios of 1∶1∶1 and 1∶2∶3. For the 1×2 photonic drop splitter, we designed two splitting ratios of 1∶1 and 1∶2. Then the performances of the PDSs were investigated with the finite-difference time-domain (FDTD) simulation technique, whose results agree well with theoretical predictions. For the drop wavelength of 1550 nm, the dimensions of the PDSs are about 10 μm×10 μm, and the free spectral range are about 36 nm, which almost covers the whole optical communication C-band window.