Sensing nano-objects, from nanoparticles to molecules, has become a crucial need in environmental monitoring, medical diagnostics, and drug development. Detection of single particles and molecules is highly desirable, as it provides specific information on size, dynamics, and interactions. Current nanophotonic implementations rely on complex optical readout schemes, limiting their application in the field. Here we demonstrate a nanophotonic fiber-tip sensor with a compact sensor footprint and a simple readout scheme. We leverage advanced design methods to simultaneously achieve a small mode volume {V_m} = 0.74 \;{(\lambda /{\rm n})^{3}}${V_m} = 0.74 \;{(\lambda /{\rm n})^{3}}$, narrow linewidth \Delta \lambda = 0.4\;{\rm nm} $\Delta \lambda = 0.4\;{\rm nm}$, and a large modulation \Delta R \approx 20\%$\Delta R \approx 20\%$ in reflection from the fiber. This unique combination of properties opens the way to sensing weak nanoscale perturbations in the vicinity of the fiber tip. In particular, we experimentally demonstrate the real-time detection of single 50 nm nanoparticles. This opens a route towards real-time sensing of single nanoparticles, and potentially single molecules, in environmental monitoring and diagnostics.

中文翻译：

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使用光纤尖端纳米光子学检测单个纳米颗粒

传感纳米物体（从纳米粒子到分子）已成为环境监测、医疗诊断和药物开发的关键需求。非常需要检测单个颗粒和分子，因为它提供了有关尺寸、动力学和相互作用的具体信息。当前的纳米光子实现依赖于复杂的光学读出方案，限制了它们在该领域的应用。在这里，我们展示了一种纳米光子光纤尖端传感器，具有紧凑的传感器占地面积和简单的读出方案。我们利用先进的设计方法，同时实现小模式体积{V_m} = 0.74 \;{(\lambda /{\rm n})^{3}}${V_m} = 0.74 \;{(\lambda /{\rm n})^{3}}$、窄线宽\Delta \lambda = 0.4\;{\rm nm }$\Delta \lambda = 0.4\;{\rm nm}$ ，以及来自光纤的反射的大调制ΔR约20%$\Delta R \approx 20\%$ 。这种独特的特性组合为传感光纤尖端附近的微弱纳米级扰动开辟了道路。特别是，我们通过实验演示了单个 50 nm 纳米颗粒的实时检测。这为环境监测和诊断中单个纳米颗粒以及潜在的单个分子的实时传感开辟了一条途径。