Fig. 11.

RCWA calculations showing differential reflectance curves for a change of the localized refractive index - 1 nm above the metallic film surface of a narrow groove gold nano-grating - from n = 1.33 to n = 1.53 upon binding of a 1nm thick target having a refractive index of 1.53 on the surface of the metallic film. The gold nano-grating had a 100 nm periodicity and the effect of nano-grating groove width ‘W’ on the differential reflectance spectra is shown for the following values of periodicity ‘P’: (a) 50 nm, (b) 100 nm, (c) 150 nm, (d) 200 nm.