基于三平行光子晶体波导的多功能功分器研究

Multifunctional Optical Splitters Based on Three Parallel Photonic Crystal Waveguides

采用时域有限差分法研究三平行光子晶体直波导的传输特性及模场分布，结合耦合模理论计算光子晶体波导的耦合系数。计算结果表明，在高频段（0．33～0．42）（ωa／2πc）的范围内两耦合波导与主波导表现出相互的能量交换，实现光耦合，耦合系数随入射波频率增加而减小；而在低频段（0．31～0．33）（ωa／2πc）的范围内，两耦合波导与主波导的传输谱图同步变化，耦合波导的传输光强均约为入射光强的四分之一。最后，提出一种采用固定波导耦合长度同时实现超微结构光均分器及1／4功分器的方案，当耦合长度取Lc=（2n＋1）π／2√2K时，两耦合波导可将高频段相应入射波实现均分，同时将低频段中的任意入射波实现1／4功分。

The propagating characteristics and mode profiles of three parallel photonic crystal waveguides are studied by using finite-difference time-domain method, and the coupling coefficient between the parallel photonic crystal waveguides is obtained with coupled-mode theory. Numerical results demonstrate that for a high frequency range of （0. 33-0. 42）（ωa/2πc）, they exchange energy with each other and the optical coupling is realized, the coupling coefficient decreased with the increase of input frequency; while at a low frequency range of （0.31 -0.33） （ωa/2πc）, the mode profiles of the coupling waveguides and main waveguide are changed synchronously, and the coupling waveguides propagating intensity occupies a quarter of the incident intensity. Finally, a solution realizing the ultracompact optical power equalizer and 1/4 optical beam splitter is proposed using a certain coupling length, when the coupling length is Lc=（2n＋1）π/2√2K, the corresponding incident wave with high frequency can be equalized, meanwhile the wave power with arbitrary frequency at low frequency can be quartered within the two coupling waveguides.