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定向耦合器是构成各类光子器件的基础元件.本文采用一种基于电场分量的全矢量有限元法,分析由梯形截面硅基水平多槽纳米线构成的定向耦合器.给出了准TE与准TM偶、奇模有效折射率、耦合长度及模场分布,揭示了其模式的混合特性及模场分布特点.分析结果表明,准TE模与准TM模的耦合长度随波导间距的增大均呈指数增长,其中准TE模的耦合长度对波导侧壁倾角的变化敏感,而准TM模的耦合长度对槽厚及槽折射率的变化敏感.恰当选择结构与材料参数,可实现两偏振态下相同耦合长度,定向耦合器在偏振无关条件下工作.
Directional couplers are the basic components of all kinds of photonic devices.In this paper, a full-vector finite element method based on the electric field component is used to analyze the directional coupler composed of multi-grooved silicon nanowires with trapezoidal cross-section. Quasi-TM, odd mode effective refractive index, coupling length and mode field distribution, revealing the mixing characteristics of the mode and the mode field distribution characteristics.The analysis results show that the coupling length of quasi-TE mode and quasi-TM mode increases with the increase of the waveguide spacing The coupling length of the quasi-TE mode is sensitive to the variation of the sidewall tilt of the waveguide, and the coupling length of the quasi-TM mode is sensitive to the variation of the groove thickness and the groove refractive index. The structure and material parameters are properly selected to achieve the two polarization The same coupling length state, directional coupler in the polarization-independent conditions.