基于倏逝波理论和光学谐振原理，研究了倏逝波在光子晶体中的存在形式及空气栅光子晶体F-P 腔的折射率传感机理，并建立谐振波长与待测气体折射率的关系模型。当入射光以大于全反射临界角的角度入射到光子晶体中，由于倏逝波的作用，在中心介质层形成F-P 腔并产生谐振，电磁场被局部增强，与待测气体充分作用，从而使该传感结构对待测气体的折射率具有较高的敏感性。利用传输矩阵理论进行数值模拟，结果表明，折射率传感的Q值可达3447.0，灵敏度可达1260.0 nm/RIU，证明该光子晶体F-P 腔折射率传感结构具有很好的传感特性，可为高精度气体折射率传感器的设计与应用提供一定的理论参考。

Based on the theory of evanescent wave and optical resonance, the existence form of evanescent wave in photonic crystal and the refractive index sensing mechanism of air gate photonic crystal F-P cavity are studied, and the relationship model between the resonant wavelength and the detected gas refractive index is established. When the incident light travels through the photonic crystal at a certain angle, which is larger than the critical angle of total reflection, as a result of the action of evanescent wave, an F-P cavity is formed in the center of dielectric layer and produces resonance. The electromagnetic field is local enhanced, and contacts with detected gas sufficiently, which causes the refractive index sensing structure has a high sensitivity with the detected gas refractive index. The transfer matrix theory is used to numerical simulation, the results show that the Q value can attain 3447.0 and the sensitivity can attain 1260.0 nm/RIU. So the proposed photonic crystal F-P cavity refractive index sensing structure has good sensing properties, and provides certain theoretical references for the design and application of high precision gas refractive index sensors.