在二维矩形阵列结构硅光子晶体中去除相间三排硅柱的两排平行硅柱形成平行线波导对。利用时域有限差分法(FDTD)模拟仿真以及数值分析研究平行线波导对之间的耦合特性，发现改变硅柱半径和背景折射率可以明显改变波导的耦合周期长度。基于此结构，提出了一种新的液体折射率检测方法，以间隔三排硅柱的平行波导对为基本结构，设计了一款液体折射率探测器。该方法与其他的液体折射率检测方法相比，具有结构紧凑、测量速度快等优势，可实现折射率的快速精确检测和仪器的小型化设计。

Two parallel line waveguides were formed by removing two lines silicon pillars which alternate with three line pillars in photonic crystal. Its coupling properties were investigated by use of Finite-difference Time-domain (FDTD) method. It is found that the coupling length between two waveguides can be changed significantly by turning the size of silicon pillar and background refractive index. A new liquid refractive index detection method was brought forward based on this research. Compared with normal liquid refractive index analyzer reported, the most important aspects are the fast detection and miniaturization of devices.