螺旋偏振矢量光束诱导的光学力矩研究  

Optical Torques Induced by the Spirally Polarized Vector Beam

作　　者：牛瑞欣 高文禹 张强 张亚楠 周源 李曼曼[1] 徐孝浩 严绍辉[1] 姚保利[1,2] NIU Ruixin;GAO Wenyu;ZHANG Qiang;ZHANG Yanan;ZHOU Yuan;LI Manman;XU Xiaohao;YAN Shaohui;YAO Baoli(State Key Laboratory of Transient Optics and Photonics,Xi'an Institute of Optics and Precision Mechanics,Chinese Academy of Sciences,Xi'an 710119,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室,西安710119 [2]中国科学院大学,北京100049

出　　处：《光子学报》2024年第11期73-82,共10页Acta Photonica Sinica

基　　金：国家自然科学基金(Nos.12274181,11974417,12127805,62135005,62335018);国家重点研究发展计划(No.2023YFF0613700)。

摘　　要：基于时域有限差分法研究了微粒在螺旋偏振矢量光束中所受的自旋光力矩,以及光波长和微粒材料、尺寸对该力矩的影响。研究结果表明,该矢量光束能诱导使微粒自转的力矩;随着棒状粒子的尺寸增大,力矩量级呈现出先增大后减小的变化趋势,棒状粒子在长度为1μm时,自旋光力矩值最大。此外,由于共振的影响,具有复杂几何结构(如六边形、手性结构)微粒所受的自旋光力矩值比棒状粒子至少大一个数量级,且随光波长的变化情况更为复杂,同时,力矩的方向也会随激发光波长和微粒尺寸发生改变,因此粒子的自旋现象更加丰富。该研究揭示了一种无需依赖光学角动量的光致微粒自转方法,补充了虚坡印廷动量对粒子旋转操控的研究,在光学微操纵领域有潜在应用价值。The Imaginary Poynting Momentum(IPM)is associated to the imaginary part of the wellknown complex Poynting vector.When light fields interact with matter,researchers usually pay attention to the real part of the complex Poynting vector,while neglect its imaginary part.However,the real Poynting vector describes only a portion of the physical mechanism underlying light-particle interaction.Recent theoretical and experimental breakthrough have been made in the study of the IPM force,which has gained increasing interest that the IPM force is independent of the optical radiation pressure and intensity gradient force.It provides a new degree of freedom for optical micromanipulation with structured light,such as vector beams,evanescent and two-wave interference fields.The IPM force can be detected directly with a Mie particle in the tightly focused Spirally Polarized Vector Beam(SPVB)when the IPM appears in the azimuthal direction.Nevertheless,the spinning optical torque caused by the vortex-like structure of IPM has not been investigated.In order to study the rotational manipulation of particles by this IPM vortex,w e use the Finite-Difference Time-Domain(FDTD)method,to investigate the spinning optical torque acting on microparticles,illuminated by the SPVB,and to study the influence of the particle material properties on the torque.The cylindrical vector beam is constructed by the in-phase superposition of the radially and azimuthally polarized vector beam.When the angle of polarization isπ/4,this cylindrical vector beam is the spirally polarized vector beam characterized by the IPM arising in the azimuthal direction.The FDTD method is a prevailing solution that can be used to solve Maxwell's equations and optomechanics for arbitrarily shaped particles.The scattering problem of arbitrary particles can be handled,so the FDTD method is characterized by high inclusivity and high accuracy.The spinning torque is computed rigorously based on the Maxwell stress tensor method,or the conservation of optical angular momentum of

关 键 词：螺旋偏振矢量光束 虚坡印廷动量 米氏粒子 自旋 光力矩 

分 类 号：TN249[电子电信—物理电子学]