SiO_2-Al_2O_3-SiO_2光子晶体缺陷腔的折射率传感特性

Refractive Index Sensing Property of SiO_2-Al_2O_3-SiO_2 Photonic Crystal Defect Cavity

为了提高光子晶体折射率传感器的灵敏度和品质因数,提出了一种基于表面波谐振原理的缺陷态光子晶体-棱镜耦合传感结构。通过分层传输矩阵法对该结构建立传感理论模型,得出古斯汉欣位移与谐振波长的变化关系,从而建立谐振波长与待测样本折射率的关系模型。以SiO2-Al2O3-SiO2作为缺陷腔来代替传统表面等离子体共振(SPR)传感器中的金膜,构成折射率敏感层;采用Al2O3作为吸收层,从而在反射光谱中得到谐振缺陷峰,通过缺陷峰值的漂移实现待测样本折射率的动态监测;以乙二醇溶液为待测样本,对该折射率传感结构的Q值及灵敏度进行了分析。结果表明,其灵敏度约为3596nm·RIU-1(RIU为相对折射率单位),Q值约为1087.7,证明了结构设计的有效性,并可为高灵敏度和高Q值折射率传感器的设计提供一定的理论指导。

To improve the sensitivity and the Q value of the photonic crystal refractive index sensor, a coupling structure combining the defect photonic crystal and the prism based on surface wave resonance theory is proposed. The sensing theoretical model is established by the layered transfer matrix method and the relationship between the Goos-Hanchen shift and the resonant wavelength is obtained, which can deduce the relationship model between the resonant wavelength and the refractive index of the sample detected. The S SiO2-Al2O3-SiO2 structure is regarded as the defect cavity, which is replaced by the gold film in conventional surface plasmon resonance （SPR） sensor. Al2 O3 is adopted as the absorbed layer, and then the resonant defect peak wavelength can be obtained and the dynamic detection of the refractive index of sample can be achieved from the shift of the resonant defect peak wavelength. The ethylene glycol is adopted as the sample detected and the Q value and the sensitivity of the refractive index sensing structure are discussed. The simulation results show that the sensitivity can attain to 3596 nm · RIU^-1 （RIU is refractive index unit） and the Q value is 1087.7 approximately, which demonstrates the effectiveness of the sensing structure. The design scheme can provide certain theoretical guidance for high sensitivity and high Q value sensor design.