光子晶體波導之傳輸行為與雙向多工元件設計

Abstract

利用平面波展開法做分析，我們發現了在一般摻雜線缺陷的光子晶體波導內部，其能量的傳輸行為是以跳躍(hopping)的方式做傳播；此外，藉由引入固態物理中的Tight-binding理論，可以描述一個光子晶體波導其傳輸行為類似一個coupled-cavity waveguide，也是以穿遂(tunneling)的方式做傳輸。 當兩個光子晶體波導彼此靠得很近時，其能帶便會由於波導之間的耦合效應，而分裂為兩種模態(even and odd)，由於發現此兩種模態在能帶中會發生能帶交叉的現象，因此，這便可以使我們找到一個decoupled frequency，利用此特殊的波導特性以及“時域有限差分法(FDTD)”之數值模擬，我們完成了双波多工元件的設計，之後更進一步地利用reduced-rod光子晶體波導其較特殊的傳播行為，而成功設計出了光通訊中的雙向多工元件。

We present an analysis of photon-transport phenomena in the 2-D triangular-lattice line-defect photonic crystal waveguide (PCW) by using plane wave expansion method. The EM field of reduced-rod waveguides is mainly localized at the defect rods. It is shown that the energy hopping through the PCW akin to the coupled-cavity waveguide. The results are illustrated by performing tight-binding curve fitting. When two PCWs close enough to each other, we found a “band-crossing” property in the dispersion relation of parallel coupled PCWs. By employing the “decoupling” at the frequency of crossing-point, we have designed a dual wavelength demultiplexer. Furthermore, by taking advantage of the particular transport behavior of reduced-rod PCW, we also design an optical bidirectional module. Both results are verified by using finite-difference time domain simulation method.