Super-resolution through illumination by diffraction-born evanescent waves

A diffraction grating in silicon with 50 nm lines and spaces is illuminated with diffraction-born evanescent waves from its transparent replica. A rotation φ between the gratings results in a set of fringes with period λf that is larger than the period of the original gratings by a magnification factor M. These fringes are induced and observed with a photon tunneling microscope having an incident illumination of 650 nm in air. This super-resolution by what may be considered a form of optical heterodyning with evanescent waves is discussed.