Wavelength-scanning method for identifying vertical position of film using surface plasmon microscopes

A wavelength-scanning method is proposed to enable surface plasmon microscopes (SPMs) to determine the vertical position of a film. Currently, it is not possible for SPMs to spatially resolve the vertical position of a layer in a multilayered sample structure because the measured value is the effective refractive index (a weighted average of the different refractive indices over the entire sensing volume). We theoretically demonstrate that the vertical position of a layer can be estimated by exploiting the fact that the sensitivity of the effective refractive index depends on the distance from the substrate surface and the wavelength.