Mao Wenbo, Li Yihang, Jiang Xuefeng, Liu Zhiwen, Yang Lan
Department of Electrical and Systems Engineering, Washington University, St Louis, MO, 63130, USA.
Department of Electrical Engineering, Pennsylvania State University, University Park, PA, 16802, USA.
Light Sci Appl. 2023 Oct 5;12(1):247. doi: 10.1038/s41377-023-01276-2.
Optical whispering-gallery-mode microsensors are a promising platform for many applications, such as biomedical monitoring, magnetic sensing, and vibration detection. However, like many other micro/nanosensors, they cannot simultaneously have two critical properties - ultrahigh sensitivity and large detection area, which are desired for most sensing applications. Here, we report a novel scanning whispering-gallery-mode microprobe optimized for both features and demonstrate enhanced Raman spectroscopy, providing high-specificity information on molecular fingerprints that are important for numerous sensing applications. Combining the superiorities of whispering-gallery modes and nanoplasmonics, the microprobe exhibits a two-orders-of-magnitude sensitivity improvement over traditional plasmonics-only enhancement; this leads to molecular detection demonstrated with stronger target signals but less optical power required than surface-enhanced-Raman-spectroscopy substrates. Furthermore, the scanning microprobe greatly expands the effective detection area and realizes two-dimensional micron-resolution Raman imaging of molecular distribution. The versatile and ultrasensitive scanning microprobe configuration will thus benefit material characterization, chemical imaging, and quantum-enhanced sensing.
光学回音壁模式微传感器是用于许多应用的有前景的平台，如生物医学监测、磁传感和振动检测。然而，与许多其他微/纳米传感器一样，它们不能同时具备两种关键特性——超高灵敏度和大检测面积，而这是大多数传感应用所期望的。在此，我们报道了一种针对这两种特性进行优化的新型扫描回音壁模式微探针，并展示了增强拉曼光谱，提供了对众多传感应用至关重要的分子指纹的高特异性信息。结合回音壁模式和纳米等离子体激元的优势，该微探针相较于传统仅基于等离子体激元的增强方式，灵敏度提高了两个数量级；这使得分子检测中目标信号更强，但所需光功率比表面增强拉曼光谱基底更低。此外，扫描微探针极大地扩展了有效检测面积，并实现了分子分布的二维微米分辨率拉曼成像。因此，这种通用且超灵敏的扫描微探针配置将有益于材料表征、化学成像和量子增强传感。
