title: Modulation of a super-Gaussian optical needle with high-NA Fresnel zone plate.
abstract: A high NA Fresnel zone plate (FZP) is studied using vectorial angular spectrum theory for realizing the sharpest possible super-Gaussian optical needle with purely longitudinal polarization illuminated by a radially polarized vector beam. Strong dispersion of the FZP results in a light field resembling a super-Gaussian optical needle by selecting an optimal FZP structural wavelength relative to the illumination wavelength and inserting a narrow comb window function into the center-shaded FZP. A 25 μm long longitudinally polarized flattop optical needle with a transverse beam width of about 0.366λ is focused at a distance of 222.5 μm away from a binary amplitude 3.46 mm diameter FZP for a 532.4 nm wavelength in free space.
authors.affiliation: Center of Ultra-precision Optoelectronic Instrument Engineering, Harbin Institute of Technology, Harbin, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
authors.forename: Jiubin
authors.initials: J
authors.lastname: Tan
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.forename: Hongting
authors.initials: H
authors.lastname: Wang