均匀球扭矩德拜级数分析

基于会聚光束所产生的扭矩来实现对小粒子的操纵已在物理学、生物学等领域得到了广泛的应用。为了分离出单个散射过程对扭矩的贡献，给出扭矩物理机理的解释，本文引入德拜级数分析了高斯波束对均匀球粒子所产生的扭矩。计算表明，当德拜项P从1取到一个足够大的值后，德拜级数计算结果与广义米氏理论结果吻合。文中重点分析了单阶P散射过程对横向扭矩的贡献，结果表明：当线极化光束入射时，P=1～5散射过程都可以产生横向扭矩，但扭矩的方向不同；当圆极化光束入射时，P=一1和0对应的扭矩远大于P=1～4对应的扭矩，且P=0过程产生与其他P过程相反方向的扭矩。

Debye series analysis of radiation torque exerted on a sphere

The radiation torque induced by a focused laser beam has been widely utilized for the optical manipulation of small particles in various fields such as physics, biology, and optofluidics. To isolate the contribution of each scattering process to the radiation torque and to clarify the physical mechanism of radiation torque, the Debye Series Expand(DSE) is introduced to analysis of the radiation torque exerted on a homogeneous sphere by Gaussian beam. When Debye mode p ranges from 1 to a value pmax large enough, the result obtained by DSE is identical to that by Generalized Lorenz-Mie Theory(GLMT). Furthermore, the radiation torque corresponding to each Debye mode p is mainly analyzed. Results show that when incident beam is linearly polarized, all scattering processes for p in 1-5 can produce a transverse torque while the directions of torque are different. When the beam is circularly polarized, the torques for p in 1 and 0 are much larger than that for p in 1-4, and the direction of torque for p in 0 is opposite with that for other mode p.