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Subwavelength generation of nondiffracting structured light beams

Nondiffracting light beams have been attracting considerable attention for their various applications in both classical and quantum optics. Whereas substantial investigations on generation of the nondiffracting beams were made, their lateral dimension is much larger than optical wavelength. Here we present both theoretically and experimentally a study of the generation of nondiffracting light beams at deep-subwavelength scale. The highly localized light field is a result of in-phase interference of high-spatial-frequency waves generated by optical sharp-edge diffraction with a circular thin film. It is shown that the generated beam can maintain its spot size below the optical diffraction limit for a distance of up to considerable Rayleigh range. Moreover, the topological structure of both the phase and polarization of a light beam is found to be preserved when it passes through the diffractive configuration, which enables generating nondiffracting vortex beams as well as transversely polarized vector beams at deep-subwavelength scale. This work opens a new avenue to manipulate higher-order vector vortex beams at subwavelength scale and may find intriguing applications in subwavelength optics, e.g., in superresolution imaging and nanoparticle manipulation.