利用倏逝波相互作用增强碳纳米管涂层侧抛光纤的NO2光学检测
Harnessing Evanescent Wave Interaction for Enhanced Optical NO2 Detection with Carbon Nanotube-Coated Side-Polished Fiber
AI总结：
本文通过实验和数值分析揭示了侧抛光纤传感器中气体诱导的导模重塑主导传感机制，并利用单壁碳纳米管薄膜实现了对NO2的偏振和厚度依赖的灵敏检测。
摘要：
基于侧抛光纤（SPF）涂覆功能纳米材料的气体监测系统因其多样化的应用而受到越来越多的关注。这些传感器的响应通常被解释为传感层的吸收调制。在这里，我们证明，在此类系统中，气体诱导的导模重塑可以主导传感机制，甚至反转光学响应的符号。使用单壁碳纳米管（SWCNT）薄膜功能化的SPF，我们观察到对NO2暴露的显著偏振和膜厚度依赖的响应。这种行为与已建立的SWCNT-NO2相互作用机制相矛盾，并且不能仅通过气体诱导的固有纳米管吸收变化来解释。数值分析表明，准确描述响应需要考虑由SWCNT折射率变化引起的纤维模式轮廓的修改。所识别的机制为基于倏逝场与功能纳米材料相互作用的光纤和集成光子传感器的设计提供了一个通用框架。
英文摘要：
Evanescent-wave photonic sensors employing nanomaterial-coated waveguides are commonly interpreted in terms of absorption modulation of the sensing layer. Here, we demonstrate that, in such systems, gas-induced reshaping of the guided optical mode can dominate the transduction mechanism and even reverse the sign of the optical response. Using side-polished optical fibers covered with single-walled carbon nanotube (SWCNT) thin films, we observe a pronounced polarization- and thickness-dependent response to NO2 exposure. For transverse electric polarization, the optical response decreases with increasing film thickness and changes sign for thicker coatings, whereas for transverse-magnetic polarization, the response increases monotonically. Numerical modeling reveals that modulation of the SWCNT complex refractive index redistributes the evanescent field, alters the mode-matter overlap integral, and controls propagation loss. These results demonstrate that evanescent-wave sensor behavior is governed not only by intrinsic material sensitivity but also by mode reshaping induced by nanomaterial coatings. The identified mechanism provides a general framework for designing fiber-optic and integrated photonic sensors based on evanescent-field interactions with tunable nanomaterials.
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