The innovative radiating structures as a conical millimeter wave FZP lens are proposed for subwavelength focusing. The results of FDTD simulation and experimental verification are discussed. It has been shown that in contrast to the flat diffractive optics the curvilinear 3D diffractive conical optics is capable of overcoming 3D Abbe barrier with a focal distance <i>F</i> greater than 2λ. 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.
© 2014 Chinese Optics LettersPDF Article