SPP-MIM hybridization meta-films for high-sensitivity and high-stability biosensing at optical fiber end-facets

Summary Achieving stable and reproducible performance has been a major challenge for nanophotonic biosensors. Literature surveys suggest that this instability strongly correlates with the nanostructured physical sensing interfaces, which we tentatively attribute to artifacts like surface gas nanobubbles. Here, we propose the hybridization of surface plasmon polaritons and a metal-insulator-metal waveguide to create a meta-film combining the flat biosensing interface characteristic of SPR with the high surface sensitivity typical of LSPR. This meta-film offers a promising solution for sealing photonic nanostructures under a flat and stable biosensing interface. We embedded the meta-film with a plasmonic crystal cavity and mounted it on a single-mode fiber's end-facet. This device demonstrated highly stable biosensing performance, achieving convincing results for biotinylated proteins down to 30 fM, with kinetics following the Langmuir model. Possessing both high sensitivity and stability, our approach provides a comprehensive solution for fiber-tip plasmonic biosensing, which is valuable for biomolecular interaction analysis and drug discovery.