Tight focusing of radially and azimuthally polarized light with plasmonic metalens

Metasurface provides extreme flexibility to manipulate the phase, polarization and amplitude of electromagnetic wave. By employing the abrupt phase shift in plasmonic nano-antenas, here we present an ultra-thin planar metalens for the azimuthally (or radially) polarized light illumination to obtain a focal spot (or doughnut-shaped focus). The designed metalens exhibits broadband frequency response at frequencies ranging from 300 to 400 THz. In addition, a tight spot size (0.47 lambda) is obtained when designed metalens with inner opaque annulus is illuminated by the azimuthally polarized light with wavelength 857 nm. It is expected that our scheme has potential applications in beam trapping, particle acceleration, integrated optics and super-resolution imaging. (C) 2015 Elsevier B.V. All rights reserved.