Comparison of Refractive-Index Sensitivities of Optical-Mode Resonances on a Finite Comb-Like Grating of Silver Nanostrips

We investigate the interplay of several different types of resonances in the scattering of light by finite comb-like nanogratings made of silver strips, in the H- and E-polarization cases. The resonances studied correspond to the localized surface plasmon modes, the periodicity-induced grating mode, and the cavity modes. They show up as Fano shapes in the total scattering cross sections and absorption cross sections. We find that the grating-mode and the cavity-mode resonances have higher values of both bulk refractive-index sensitivity and figure-of-merit than the localized-surface-plasmon resonances, in the visible band.