Two-dimensional array of plasmonic V-shaped grooves for sensing applications

We numerically analyzed the refractive index sensing performance of the two-dimensional array of plasmonic V-shaped grooves. The structural parameters are optimized to show a sharp and large reflectance dip with desired sensing region (n=1.33). Acquiring the sensitivity of the environmental refractive index as 400 nm/RIU in the visible region, FWHM of the dip is ∼5 nm. It shows that the proposed structure has extreme value of quality factor and good extinction ratio. The localized mode has the hot spot at the bottom of the grooves so that localized sensing based on magnetic field enhancement is possible. Moreover, the localized mode is dependent on the tapered angle of the grooves, not the opening ratio. The performance of the dual V-shaped grooves is also discussed. The array of the closely located grooves has nearly identical reflectance spectra but a moderate amount of dip shift exists. As well as obtaining refractive index sensing by this configuration, magnetic field hot spot generation by coherent excitation can be applied to highly localized sensing and enhancing nonlinear processes.