High-Sensitivity Fiber Tip Sensor Based on Dark Plasmonic Resonance Mode

This study proposes a high-sensitivity optical fiber tip sensor based on subradiant dark mode achieved by coating well-dispersed Au nanoparticles (AuNPs) on the thin fiber core cylinder waveguide. Due to the propagation-induced phase delay and dipole coupling, the AuNPs support dark mode of localized surface plasmon resonance (LSPR). The resonance wavelength is insensitive to the length of cylinder waveguide and uniformity of interparticle distance. Therefore, it can be conveniently fabricated by simple chemical etching and self-assembly methods. A sensitivity of 2019.8 nm/RIU is obtained experimentally, about 3~10 times higher than the reported fiber tip LSPR transducers. These results indicate that combining dark mode with fiber tip is a promising candidate for constructing high-performance plasmonic sensors.