Sun Li-Peng, Li Jie, Tan Yanzhen, Gao Shuai, Jin Long, Guan Bai-Ou
Opt Express. 2013 Nov 4;21(22):26714-20. doi: 10.1364/OE.21.026714.
We demonstrate the bending effect of microfiber on interference fringes in a compact taper-based modal interferometer and sensitivity for refractive index (RI) measurement. For the bend curvature ranging from 0 to 0.283 mm(-1), the measured RI sensitivity distinctively increases from 342.5 nm/RIU (refractive-index unit) to 1192.7 nm/RIU around RI = 1.333 and from 3847.1 nm/RIU to 11006.0 nm/RIU around RI = 1.430, respectively. Theoretical analysis reveals that such enhancement is determined by the dispersion property of the intermodal index rather than other parameters, such as the variation of the straightforward evanescent field. The magnitude of sensitivity varies as a function of the microfiber bend curvature. Approaching a critical curvature (the intermodal-index dispersion factor approaches zero), the sensitivity is significantly enhanced, exhibiting great potential in RI sensing areas.
我们展示了微纤维对紧凑型锥形模态干涉仪中干涉条纹的弯曲效应以及用于折射率（RI）测量的灵敏度。对于弯曲曲率范围从0到0.283 mm⁻¹，在RI = 1.333附近，测得的RI灵敏度分别从342.5 nm/RIU（折射率单位）显著增加到1192.7 nm/RIU，在RI = 1.430附近从3847.1 nm/RIU增加到11006.0 nm/RIU。理论分析表明，这种增强是由模式间折射率的色散特性决定的，而不是由其他参数决定，例如直接消逝场的变化。灵敏度的大小随微纤维弯曲曲率的函数而变化。接近临界曲率（模式间折射率色散因子接近零）时，灵敏度显著增强，在RI传感领域展现出巨大潜力。
