Abstract
The sensitivity of the wavelength position of localized surface plasmon resonance (LSPR) in metal nanostructures to local changes in the refractive index has been widely used for label-free detection strategies. Tuning the optical properties of the nanostructures from the visible to the infrared region is expected to have a drastic effect on the refractive index sensitivity. Here, we theoretically investigate the optical response of a newly designed plasmonic interface to changes in the bulk refractive index by the finite difference time domain method. It consists of a structured interface, where the planar interface is superposed with dielectric pillars 30 nm in height and 125 nm in length with a separation distance of 15 nm. The pillars are covered with U-shaped gold nanostructures of 50 nm in height, 125 nm in length, and 5 nm of gold base thickness. The whole structure is finally covered with a 5-nm thick dielectric layer of n2 = 2.63. This plasmonic structure shows bulk refractive index sensitivities up to 1750 nm/RIU (RIU : refractive index unit) in the near infrared (λ = 2621 nm). The enhanced sensitivity is a consequence of the extremely enhanced electrical field between the gold nanopillars of the plasmonic interface.
Published Version
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