使用分波多工 (wavelength-division multiplexing) 之通訊系統能對系統中可利用的頻寬作較有效的運用。由於折射係數呈週期性結構的光子晶體具有光子能隙，頻率落入光子能隙區間中的光會因此而無法在光子晶體中傳遞。我們可利用在光子晶體中置入缺陷結構來控制光傳遞的頻率與方向且利用光子晶體所製作的分波多工元件之體積只需幾個微米的大小等級。因此，這種積體化光子晶體之波長塞取濾波器相當適合用於分波多工之光通訊系統中。

　　到目前為止已有許多種通道之波長塞取濾波器被提出。基於容易設計與製作的考量，我們選擇利用直接耦合結構與側邊耦合結構來實現多通道之波長塞取濾波器。爲了改善具備直接耦合結構或側邊耦合結構的多通道波長塞取濾波器的傳輸效能，我們在輸入波導的末端置入一反射器。除此之外，若我們可結合直接耦合結構及側邊耦合結構則多通道波長塞取濾波器幾何型態的調整將變得更有彈性，並且也可以達到更好的傳輸效能。利用有限時域差分法 (finite-difference time-domain method) 可以計算此篇論文中所提出的濾波器之傳輸效能。

　The use of a Wavelength-division multiplexing (WDM) based communication system allows for better utilization of the spectral bandwidth resources available to the system. Photonic crystals exhibit photonic bandgap (PBG) due to the periodic structure of the refractive index and light propagation with a range of frequencies within the PBG is consequently prohibited. In addition, we can control the light propagation both with respect to frequency and direction by introducing defect in photonic crystals and WDM devices based on photonic crystals can be achieved on a much smaller size about several micrometers. Therefore the operations of such ultra-compact photonic crystal-based channel add/drop filter are suitable to be used in WDM optical communication systems.

　UP to present, many kinds of channel add/drop filter have been proposed. For the reason of easily design and fabricate, we chosen direct coupling structure and side coupling structure to realize multi-channel add/drop filter. In order to improve the add/drop efficiency of the multi-channel add/drop filter with direct coupling structure or side coupling structure, we introduced a reflector in the end of the bus waveguide. Moreover, if we combine both direct coupling structure and side coupling structure, tuning the geometrical pattern of multi-channel add/drop filter becomes more flexible and higher add/drop efficiency can be achieved. The transmission efficiency of the proposed filter in this thesis has been calculated using the finite-difference time-domain (FDTD) method.

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