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将相互耦合的3平行光子晶体单模波导看成一个多模干涉系统,通过研究二维正方晶格光子晶体波导多模干涉的自映像效应,优化设计了一种新型1×2光子晶体波导定向耦合分束器,采用时域有限差分法对其传输特性进行模拟分析。设计过程中,根据多模干涉耦合区中周期出现的双重像的位置确定两个单模输出波导的位置,通过改变输出波导和耦合区连结的一个介质柱位置构成波导微腔结构,改变耦合区中的模场分布,实现模式匹配,从而明显减小分束器的反射损耗。计算结果表明,移动介质柱距离输出单模波导和多模波导连结处1.85a位置处时,对于波长为1.55μm的入射光,该分束器的透射率可高达99.04%。
The coupled 3 parallel photonic crystal single mode waveguide is considered as a multimode interference system. By studying the self-mapping effect of 2-D square lattice photonic crystal waveguide multimode interference, a new type of 1 × 2 photonic crystal waveguide orientation Coupling beam splitter, the use of time-domain finite difference method to simulate the transmission characteristics. In the design process, the positions of the two single-mode output waveguides are determined according to the positions of the double images in the period of the multi-mode interference coupling region. The structure of the waveguide microcavity is formed by changing the position of a dielectric column connected with the output waveguide and the coupling region to change the coupling region In the mode field distribution, to achieve pattern matching, thereby significantly reducing the beam splitter reflection loss. The calculated results show that the transmittance of the beam splitter can reach as high as 99.04% for the incident light with the wavelength of 1.55μm when the moving medium column is located at the position of 1.85a from the output of the single mode waveguide and the multimode waveguide.