Ultrafast Surface Plasmon Resonance Sensing via Dual‐Comb Spectroscopy

Surface plasmon resonance (SPR) is a powerful technique widely applied in biochemistry, drug screening, and environmental monitoring for high‐sensitivity, label‐free, real‐time detection of biomolecules and their interactions. Enhancing key performance characteristics, including sensitivity, resolution, dynamic range, and measurement speed, is essential for rapid and accurate detection of low‐concentration analytes in complex samples. A broader dynamic range is also required to support simultaneous detection of multiple samples. Here, we demonstrate the significant potential of dual‐comb spectroscopy for SPR phase sensing, enabling ultrarapid detection while maintaining practical refractive index resolution and dynamic range. We achieved broadband SPR interference spectral measurements with a 10‐µs refresh time, enabling rapid detection of sodium chloride solutions at varying concentrations with a single‐acquisition refractive index resolution of 1.47 × 10 −4 refractive index unit (RIU). The refractive index resolution was further improved to 4.36 × 10 −6 RIU with 100 ms averaging, and a dynamic range of 10 −3 RIU was achieved. In addition, we monitored NaCl diffusion in water and rapid liquid–liquid and liquid–gas switching under high‐speed flow conditions, capturing refractive‐index dynamics as fast as approximately 4 ms with a temporal resolution of 100 µs. This technique opens avenues for investigating ultrafast dynamic processes.