表面覆膜波导光栅共振光谱特性及传感机理分析

基于波导光栅共振原理和古斯-汉欣(Goos-Hänchen)位移理论，提出一种表面覆膜波导光栅传感结构，并研究其共振光谱特性。通过在光栅表面涂覆低折射率聚合物功能膜层优化其共振光谱特性，选用多孔硅作为待测物承载单元，可以使光学探针更充分地接触待测样本，从而提高其检测性能。根据波导光栅共振相位条件，建立了共振波长和样本折射率之间的数学模型，通过检测共振位置的改变进而对样本浓度进行检测。研究表明，该表面覆膜波导光栅传感结构具有线型对称和窄线宽的共振光谱特性，可实现高品质因数(Q值)和高灵敏度的传感特性，其Q值为1 488，对折射率的检测极限可达5×10-4 RIU(RIU为折射率单位)。通过检测不同浓度的葡萄糖溶液对其传感特性进行验证分析，结果表明，共振波长与葡萄糖溶液浓度之间具有良好的线性关系，对葡萄糖溶液的检测灵敏度为1.12nm/1%，证明了该表面覆膜波导光栅传感结构的有效性，可以用于对低浓度样本溶液的实时动态监测，并为波长调制型光学折射率传感器的研究提供理论指导。

Resonance Spectral Characteristic and Refractive Index Sensing Mechanism of Surface Coated Waveguide Grating

Based on the resonance principle of waveguide grating and Goos-Hänchen displacement theory, a refractive index sensing model of surface coated waveguide grating is proposed, and the resonance spectral characteristics are analyzed. In addition, the resonance spectral characteristics are optimized by coating the polymer film upper the grating, the porous silicon is used as the sensing unit, the samples detected and electromagnetic wave will contact fully and the sensitivity can be improved effectively. According to the phase condition of the waveguide grating resonance, the relationship between the resonance wavelength and the refractive index of samples detected is established, and the concentrations of samples can be detected by detecting the shift of the resonance wavelength. The results show that the surface coated waveguide grating sensing structure has the sensing characteristics of high quality factor and high sensitivity, the quality factor of the surface coated sensing structure is 1 488, and the detection limit of refractive index is 5×10-4 RIU. Moreover, the sensing characteristics are analyzed by detecting different concentrations of glucose solution, the results show that there is a good liner relationship between resonance wavelength and the concentrations of the glucose solution, and the sensitivity of the glucose solution is 1.12 nm/1%, the validity of the sensing structure is proved. The surface coated waveguide grating sensing structure can be used to detect the samples with low concentrations and provide theoretical guidance for the further study of the optical refractive index sensors.