本研究目的在設計一個具有高能量強度對比的分波多工器元件。此元件的結構為一個可侷限三個模態之波導管，在波導管中央沿著波傳遞的方向蝕刻一條長凹槽，此長凹槽可提高波導管的色散性，並縮短元件的分波距離。元件的設計、模擬與效能分析是利用二維情況下的有限差分時域法（Finite Difference Time Domain, FDTD），分析的結果顯示此分波多工器能有效地使得波長為1530 nm與1570 nm的兩光波在短距離內分開，且能量強度對比可分別達到27.2 dB與31.5 dB，而嵌入損耗僅僅小於0.5 dB。元件設計中涉及的理論是多模干涉自我映射定律（Self-Imaging Principle），文中會對多模干涉以及用於模擬分析的FDTD數值模擬方法詳加討論。

　　In this thesis, a novel wavelength division multiplexer (WDM) device of high energy intensity contrast is designed. The structure of this device based on multi-mode interference(MMI) is a three-moded waveguide etched centrally along the propagation direction of optical wave. The two-dimensional finite difference time domain(FDTD) is used for the design, simulation and analysis of this device. The result of simulation and analysis shows 1530nm and 1570nm can be divided effectively in a short distance in this three-moded device, and high energy intensity contrast and very low insertion loss are provided by this device. The energy intensity contrasts of 27.2dB and 31.5dB can be achieved for the wavelengths 1530nm and 1570nm respectively, and both the insertion loss below 0.5dB can be achieved for the wavelengths 1530nm and 1570nm. The theory of MMI based on self-imaging principle and the FDTD tool for simulation and analysis are introduced in the theory section.

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