定向耦合器由多个光子晶体单模波导平行、邻近放置构成。在输入光场对称入射时, 根据自映像原理数值分析了光在其中的传播行为。基于此结构, 以3通道为例, 设计了超微多路光分束器, 仅仅通过对称地改变耦合区中两个介质柱的折射率, 使光场在横向发生重新分布, 实现了输出能量的均分或自由分配。这种调制方法简单且输出效率更高。

A directional coupler is composed of multiple photonic crystal monomode waveguides placed in parallel and adjacent to each other. When the input optical field is symmetric to the incidence, its propagations in this system are numerically analyzed in accordance with the self-imaging principle. On the basis of this structure, an ultracompact multichannel, say 3-channel, beam splitter is designed and the optical field is transversely redistributed simply by symmetrically changing the refractive indexes of two dielectric rods in the coupling region, realizing the uniform or free distribution of the output energy. This kind of modulation is simple and more efficient.