为实现高精度和高灵敏度的折射率测量,采用微米级氢氟酸液 滴化学腐蚀的方法制作非对称的微纳光纤Fabry-Perot (FP)谐振腔,具有波导尺寸小、损耗低、双折射率高和腔Q值高等优点。不同正交偏振方向的谐振模式对 外界折射率变化具有不同的响应,沿光纤快轴和慢轴方向的模式折射率灵敏度分别为133.8 nm/RIU、 117.1 nm/RIU, 快慢轴方向的温度灵敏度均为0.012 nm/°C, 通过光谱仪监测两束偏振光的 波长差可实现温度独立的折射率测量。采用不同FP腔参数的光纤 传感器进行实验研究,结果表明光纤FP传感器腔直径越小,腐蚀占腔长比越高,其折射率灵敏度越高。

To achieve high accuracy and high sensitivity measurement of refractive index, an asymmetric micro-nano fiber Fabry-Perot resonator is fabricated using micron size hydrofluoric(HF)-acid droplet chemical etching method. The fabricated structure is featured with small size, low loss, large birefringence and high Q value. The guided modes along the orthogonal polarizations present different refractive index (RI) responses. The measured RI sensitivities are 133.8 nm/RIU and 117.1 nm/RIU for the modes along the fast and slow axis, respectively. The temperature sensitivity is 0.012 nm/°C for the two polarization modes. The temperature independent refractive index measurement can be realized by monitoring the wavelength difference of two polarized light with spectrometer. Experiment investigation is carried out with optical fiber sensors with different FP cavity parameters. Results show that the smaller the cavity diameter of fiber FP sensor is, the higher the corrosion rate is, and the higher the refractive index sensitivity is.