本論文以SOI結構為基礎，提出一個改良的極化分離器，利用肋狀波導去耦合現象來設計對稱型定向耦合器，在結構中新增一個材料與波導結構相同的平台，增加去耦合機制，將去耦合現象及TM模態截止效應分開，可避免高階模態產生，且有效的將元件尺寸縮小，使TM模態達到不耦合，而TE模態因對稱波導的折射率相等，在設計得當的耦合距離滿足相位匹配條件，將耦合至另外一根波導中，達到極化分離的效果。首先固定波導芯的寬度與高度，設計了不同的平台高度與對應板狀結構高度，板狀結構高度80nm、平台高度超過160nm會出現高階模態。透過分析交叉極化耦合效應發現，隨著平台高度與板狀結構高度下降，都可有效的抑制交叉極化耦合效應，最終板狀結構高度80 nm，平台高度125 nm，為結構參數。

Based on the SOI structure, this paper proposes an improved polarization splitter, which uses the decoupling phenomenon of the rib waveguide to design a symmetric directional coupler. A platform with the same material as the waveguide structure is added to the structure, and the decoupling mechanism is added. , the decoupling phenomenon and the TM mode cut-off effect are separated, which can avoid the generation of high-order modes, and effectively reduce the size of the component, so that the TM mode can be uncoupled, while the TE mode is equal to the refractive index of the symmetric waveguide. If the proper coupling distance satisfies the phase matching condition, it will be coupled to another waveguide to achieve the effect of polarization separation. Firstly, the width and height of the waveguide core are fixed, and different platform heights and corresponding plate-like structure heights are designed. The plate-like structure height is 80 nm, and the platform height exceeds 160 nm, high-order modes will appear. By analyzing the cross-polarization coupling effect, it is found that the cross-polarization coupling effect can be effectively suppressed as the height of the platform and the plate-like structure decrease. The final plate-like structure height is 80 nm and the platform height is 125 nm, which are the structural parameters.