The minimum number belts of DOE for Bessel–Gauss beams to generate a strong longitudinally polarized beam

• DOI: 10.1007/s00340-017-6852-2
• Publication Date: 2017-11-04T06:20:02Z
• Authors: Jian Fu; Ying Wang; Peifeng Chen
• Keywords: Bessel beam; Aperture (computer memory); M squared; Gaussian beam

In this paper, we minimize the number of belts on the diffractive binary optical element (DOE) to generate a strong longitudinally polarized beam by focusing a radially polarized Bessel–Gaussian beam. Based on a combination of the three-belt DOE and a high-numerical aperture parabolic mirror focusing system, a needle of strong longitudinally polarized beam can be achieved. The transverse full width at half maximum of this longitudinally polarized beam is 0.40 λ and the longitudinal field power fraction reaches 85%. In alternative focusing elements, three belts are the minimum number of the DOE for Bessel–Gauss beams.