Plasmonic-photonic hybrid configuration on optical fiber tip: Toward low-cost and miniaturized biosensing probe

Owing to the label-free and real-time biosensing advantages, the nanostructured plasmonic biosensors on optical fiber tips have attracted increasing attention as potential plug-and-play remote sensing probes available for limited environments. Various nanostructures have been developed by either top-down or bottom-up approaches on optical fiber tips. However, a trade-off between the sensing performance and manufacturing cost of these plasmonic fiber-optic sensors usually limited their further application. In this context, we propose and systematically investigate a novel plasmonic-photonic hybrid configuration, which dramatically boosts the sensing performance and simplifies the fabrication process. The hybrid configuration integrated onto the fiber tip consists of a dielectric coating acting as the photonic cavity and dispersed Au nanoparticles serving as the plasmonic nanostructures. As a result of the coupling between localized surface plasmon resonance and the cavity interference mode, a hybrid plasmonic-photonic resonance is successfully excited and proved to have serval unique features including enhanced sensitivity, high stability, and precise tunability of the resonance frequencies. Finally, as a proof-of-concept for biosensing, we experimentally demonstrate that the proposed fiber-optic sensors can achieve real-time monitoring of the biomolecular binding interactions at nanomolar concentration, confirming the potential of the plasmonic-photonic configuration in developing miniaturized high-performance sensing probes.