Superoscillatory diffraction-free beams

It is widely known that any beam with subwavelength characteristics will diffract very fast and these features will not propagate into the far field. This is due to the existence of evanescent waves, which diffract in the near field. By using the counter-intuitive effect of superoscillations we show that it is possible to create a superoscillatory diffraction free beam by superimposing already known diffraction-free solutions (Bessel beams for example) of Helmholtz equation. Such optical beams do not contain any evanescent waves and can propagate practically undistorted carrying these subwavelength features into the far field. Superoscillations have been recently studied and introduced to optics in the context of superresolution, and subwavelength focusing.