Spectral properties of 3D diffractive lenses with 3D subwavelength focusing spot

The innovative radiating structures as a conical millimeter wave FZP lens are proposed for subwave-length focusing at different wavelength. The results of experimental verification are discussed. It has been shown that in contrast to the flat diffractive optics the curvilinear 3D diffractive conical optics allows for over-coming 3D Abbe barrier at the bandwidth at least of ±20% with focal distance F more than F>40λ. The focal intensity distribution for such type of lenses is not circularly symmetric and thus the focal spot in the high numerical aperture case is no longer an Airy pattern. These results may find useful applications in optical microscopes, including “reverse-microscope”, nondestructive testing, microoptics, and nanooptics.