三环非均匀混合偏振同轴矢量光束的聚焦特性

基于Richards-Wolf矢量衍射积分公式,数值分析了同轴三环非均匀混合偏振矢量光束经过高数值孔径透镜的聚焦特性。该矢量光束由同轴三环局域线偏振矢量光束通过一个相位延迟角为δ的液晶相位延迟器产生,光束偏振变为包含线偏振、圆偏振和椭圆偏振的混合态。同轴三环局域线偏振矢量光束的偏振分布是由径向向内偏振的外环光束、径向向外偏振的内环光束和线偏振方向与径向方向夹角为φ2的中环光束构成。数值模拟结果显示该混合偏振矢量光束的聚焦强度分布与参数φ2和相位延迟角δ密切相关,当选取适当的φ2和δ时,在焦平面附近产生沿光轴方向的三维多点光俘获结构——暗光链,这在光学微操纵领域具有潜在的应用价值。

Focusing Features of Concentric Three-Ring Non-Uniform Mixing Polarization Vector Beams

The focusing property of concentric three-ring non-uniform mixing polarization vector beams through a high numerical aperture is theoretically investigated near the focal plane by using Richards-Wolf vectorial diffraction method. This kind of vector beams can be obtained by letting a concentric three-ring local linearly polarized cylindrical vector beam passes through a phase retarder with a phase angle δ. The three ring local linearly polarized cylindrical vector beam consists of the outer circle whose polarization is along the radially inward, the inner circle portion whose polarization is along the radially outward and the centray circle whose polarization direction has an angle φ2 with radial direction. The results of the numerical simulation show that the focusing intensity distribution of the non-uniform mixing polarization vector beams is closely related with parameters φ2 and δ. It is shown that the 3D dark optical chain along optical axis can be obtained near the focus by modulating the value of φ2 and δ, which has potential application in the optical micro-manipulation.