Toward the subdiffraction focusing limit of optical superresolution

A superresolving three-zone plate is applied to a Fresnel diffractive lens. It is shown that for radial incident polarization this combination produces a focal spot approaching superresolution allowed subdiffractive limit of 0.36 lambda/NA for focusing. For media responsive to longitudinal field component only, our phase engineering scheme results in a focal spot size of 0.368 lambda/NA. When used with a solid immersion lens, the scheme can generate the smallest focal spot available for passive optics. (c) 2007 Optical Society of America.