Li Manman, Yan Shaohui, Yao Baoli, Liang Yansheng, Zhang Peng
Opt Express. 2016 Sep 5;24(18):20604-12. doi: 10.1364/OE.24.020604.
Focusing fields of optical vortex (OV) beams with circular or radial polarizations carry both spin angular momentum (SAM) and orbital angular momentum (OAM), and can realize non-axial spinning and orbiting motion of absorptive particles. Using the T-matrix method, we evaluate the optical forces and torques exerted on micro-sized particles induced by the OV beams. Numerical results demonstrate that the particle is trapped on the circle of intensity maxima, and experiences a transverse spin torque along azimuthal direction, a longitudinal spin torque, and an orbital torque, respectively. The direction of spinning motion is not only related to the sign of topological charge of the OV beam, but also to the polarization state. However, the topological charge controls the direction of orbiting motion individually. Optically induced rotations of particles with varying sizes and absorptivity are investigated in OV beams with different topological charges and polarization states. These results may be exploited in practical optical manipulation, especially for optically induced rotations of micro-particles.
具有圆偏振或径向偏振的光学涡旋（OV）光束的聚焦场同时携带自旋角动量（SAM）和轨道角动量（OAM），并且可以实现吸收性粒子的非轴向自旋和轨道运动。利用T矩阵方法，我们评估了由OV光束施加在微米尺寸粒子上的光学力和扭矩。数值结果表明，粒子被困在强度最大值的圆周上，并分别经历沿方位角方向的横向自旋扭矩、纵向自旋扭矩和轨道扭矩。自旋运动的方向不仅与OV光束的拓扑电荷符号有关，还与偏振态有关。然而，拓扑电荷单独控制轨道运动的方向。在具有不同拓扑电荷和偏振态的OV光束中研究了不同尺寸和吸收率的粒子的光致旋转。这些结果可用于实际的光学操纵，特别是用于微粒的光致旋转。
