基于衍射受限矢量光管场的离散式复振幅滤波器的设计

提出一种离散式的复振幅光瞳滤波器,用于构建大数值孔径系统下柱对称偏振矢量光束的特殊聚焦光场。输入角向偏振矢量光束,经圆对称的6个离散环带复振幅滤波器滤波后聚焦。该滤波器半径已归一化,各环带具有不同透射振幅,外围两环带有相同的相位延迟,其余相邻透射环带间π反相。在聚焦区可获得超长(大于8λ)的衍射受限"光管"场。该"光管"场为中空的纯角向偏振矢量光场,管中心沿轴向无光场分布,光管横向直径(约0.31λ)在亚波长量级,"光管"管壁为沿轴向平坦分布的角向偏振矢量场,无轴向旁瓣。该复振幅滤波器可用于构建特殊三维矢量光场以及利用该光场进行粒子捕获和操控。

Discrete Complex Pupil Filter for Diffraction Limited Three-Dimensional Optical Tube Field

A discrete complex pupil filter is proposed to create focused field using cylindrical beams in the high numerical aperture(NA) system.The radius of this filter is normalized to 1.It consists of six discrete transmitted annular zones with different amplitudes and there zones are shifted by a π phase retardation in neighboring zones except for the same retardation in the two outermost zones.The polarization pattern and intensity of the incident azimuthally polarized beam can be modified by the filter and then focused by the high NA lens.An ultra-long(longer than 8λ) diffraction limited three-dimensional optical tube with azimuthal polarization spiraling around z-axis can be created.The center of the optical tube field is null along the axial direction.And the radius of the tube determined by the transverse full width at half maximum(FWHM) of this focused field is 0.31λ in the focal plane and remains nearly constant throughout the total depth of the tube.This complex pupil filter will meet applications in three-dimensional tailoring of focused field and trapping and manipulation of particles.