Optical Trapping of Double-Ring Radially Polarized Beam with Improved Axial Trapping Efficiency

• Published in: Chinese physics letters Vol. 27; no. 10; pp. 224 - 227
• Main Author: 姚保利 严绍辉 叶彤 赵卫
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.10.2010
• Subjects: 传播方向; 捕集效率; 线性偏振光
• ISSN: 0256-307X; 1741-3540
• DOI: 10.1088/0256-307X/27/10/108701

Radially polarized beams, focused by a high numerical aperture （NA） objective, have non-propagating fields along the propagation axis in the focal region, which leads to a higher axial trapping efficiency in comparison with linearly polarized beams. We propose a design for converting a lowest-order radially polarized beam （R-TEM01） to a double-ring radial polarization distribution （DR R-TEM01） through a specially designed polarization rotator. The phases of the two rings of this beam differ by π. Numerical results evaluated by rigorous T-matrix method show that the DR R-TEM01 beam can improve the axial trapping efficiency compared with the R-TEM01 beam, provided that the size of trapped particles is of order of the wavelength of the beam.