Generating a Superoscillation Three-Dimensional Hollow Spot by Polarization Manipulation

A wide variety of practical applications utilize three-dimensional (3D) hollow spots. To improve their performance, it is critical to independently control the transverse and longitudinal size of a 3D hollow spot. Here, we propose a method of creating a superoscillation 3D hollow spot by properly engineering the spatial polarization distribution. A cylindrical vector wave can be generated and the transverse and longitudinal sizes of the 3D hollow spot can be independently controlled by individually optimizing the wave fronts of the radial and azimuthal components in the cylindrical vector wave. A cylindrical vector metalens integrated with the functions of polarization conversion and wave-front manipulation is optimized and fabricated. The generated 3D hollow spot is experimentally demonstrated with a transverse size of (0.336 +/- 0.005)A and a longitudinal size of (1.170 +/- 0.005)A. Our method provides an easy and practical approach to generate a 3D hollow spot with a subwavelength transverse size, which can be intriguing for nanoparticle manipulation and in nanomicroscopy.