High-sensitivity plasmonic sensor by narrowing Fano resonances in a tilted metallic nano-groove array

Plasmonic sensors exhibit enormous potential in the areas of environmental monitoring, biomedical diagnostics, healthcare, food safety, security, and chemical reactions. However, the large bandwidths of surface-plasmon response spectra greatly reduce the sensitivities and detection limits of plasmonic sensors. Herein, we propose to tilt a metallic nano-groove array to reduce linewidths of Fano resonances, and the figure of merit (FOM) of a refractive index sensor is greatly increased. The Fano resonances stem from interference between narrow SPP resonant modes and a broad LSP mode in the metallic nano-groove array. When tilting the metallic nano-groove array, new Fano resonances emerge, greatly compressing the linewidth of Fano resonance of interest to similar to 1.1 nm in the simulation. Experimentally, a narrow Fano resonance with a linewidth of Delta lambda approximate to 2.5 nm is achieved, and a high-FOM (FOM approximate to 263) plasmonic sensor is demonstrated. This value of FOM is more than 4.7 times that (FOM <= 55) of Fano sensors based on SPP modes, and it is even approximately twice that (FOM approximate to 140) of the previous Fano sensor based on Wood's Anomaly. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement