Photonic crystal fibers (PCFs), providing ingenious microfluidic channels and intense light guidance, have many advantages in the detection of three-dimensional surface-enhanced Raman scattering (SERS). In solid-core PCFs, the light interacts with the sample in the form of an evanescent field, which is weak and limits the SERS detection performance. In this paper, we propose a new mechanism based on avoided crossings between the fiber core mode and the surface mode, which greatly enhances the laser power ratio in the liquid channels and improves the SERS sensitivity. Numerical results show that the intensity in the liquid channels can be increased from 2.8 % to 42 %. To realize this avoided-crossing effect in PCFs experimentally, the silver mirror reaction was optimized which can decorate discrete and densely distributed silver nanoparticles on the hydroxylated surface of the microfluidic channels in less than 15 min. The resulting SERS-active suspended-core PCF has ultra-high sensitivity, with a detection limit of 10⁻¹² M, and an enhancement factor of 10¹⁰ for crystal violet solution. It also provides good stability and reproducibility with a relative standard deviation of 4.8 %. This ultra-sensitive and highly reproducible PCF-SERS probe has great potential for application in rapid in-situ detection.

光子晶体光纤 (PCF) 提供巧妙的微流体通道和强光引导，在检测三维表面增强拉曼散射 (SERS) 方面具有许多优势。在实芯 PCF 中，光以渐逝场的形式与样品相互作用，这很弱并且限制了 SERS 检测性能。在本文中，我们提出了一种基于避免光纤芯模和表面模交叉的新机制，大大提高了液体通道中的激光功率比，提高了 SERS 灵敏度。数值结果表明，液体通道中的强度可以从 2.8% 增加到 42%。为了通过实验实现 PCF 中的这种避免交叉效应，优化了银镜反应，可以在不到 15 分钟的时间内在微流体通道的羟基化表面上装饰离散且密集分布的银纳米颗粒。由此产生的 SERS 活性悬浮核心 PCF 具有超高灵敏度，检测限为 10^-12 M，结晶紫溶液的增强因子为 10 ¹⁰。它还具有良好的稳定性和重现性，相对标准偏差为 4.8%。这种超灵敏和高重现性的 PCF-SERS 探针在快速原位检测中具有巨大的应用潜力。