Optimization of the enhanced evanescent wave for near-field microscopy

Near-field microscopy usually uses an evanescent wave as an illumination source on a sample. An enhanced evanescent wave can be obtained at the surface of a multilayer thin-film coating system due to the optical tunnelling effect. It can improve the illumination power by several orders of magnitude in near-field microscopy. The enhancement of an evanescent wave is related to the thickness and refractive indices of the thin film layers as well as the incident angle and wavelength of the illumination source. In this paper, Optimization of these parameters is studied in details under resonance conditions, and some experimental results are also presented.