本論文中，我們提出兩種二維雙輸入雙輸出光子晶體分光器。其結構由兩正交之光子晶體波導在正方晶格之中。兩波導相交處之結構被改變去控制電磁波的分流比例。空氣柱和介電質柱的光子晶體皆被研究，而且其機制也被討論。而以光子晶體形成的馬氏干涉儀的特性(強度調變器)也被研究。In this wok, we propose two novel two-dimensional photonic crystal beamsplitters with two input ports and two output ports. The structure consists of two orthogonal-crossing line defects in square lattice. The intersection of two orthogonal photonic crystal waveguides was modified to control the splitting ratio of the electromagnetic waves. The photonic crystal beamsplitters with air-holes and dielectric pillars are studied. The mechanisms of the light splitting in the photonic crystal beamsplitters are discussed. The characterization of the Mach-Zehnder interferometers (intensity modulator) using the photonic crystal beamsplitters are investigated.