Improved sensitivity in a T-shaped nanodimer plasmonic sensor

Fano resonance can exist in a T-shaped nanodimer due to interaction between the bright mode of the short nanoparticle and the dark mode of the long nanoparticle. The coupling between the bright and dark modes is studied in detail and compared with a line-shaped nanodimer. The coupling strength of the T-shaped nanodimer is enhanced due to the high density of localized electromagnetic states. It is found that the enhanced coupling strength in the T-shaped nanodimer can improve the sensitivity of the system. The different spectral responses to different spatial locations of the T-shaped nanodimer provide an effective way to monitor refractive index changes both spectrally and spatially.