Analysis of radiation force on a uniaxial anisotropic sphere by dual zero-order Bessel beams

Abstract

Based on the generalized Lorenz–Mie theory (GLMT), a theoretical approach is introduced to study the radiation force exerted on a uniaxial anisotropic sphere illuminated by dual zero-order Bessel beams (ZOBBs). The beams propagate with arbitrary direction, and are expanded in terms of the spherical vector wave functions (SVWFs) in the particle coordinate system using the coordinate rotation theorem. The total expansion coefficients of the incident fields are derived by superposition of the vector fields. Applying the Maxwell’s stress tensor, the analytical expressions of the radiation forces on a homogeneous absorbing uniaxial anisotropic sphere are derived. Comparing the radiation forces of dual ZOBBs with those results of dual ZOBBs simplified into single ZOBBs and dual plane waves, the accuracy and correctness of the theory are verified. In order to study the equilibrium state, the effects of beam parameters, particle size parameters, and anisotropy parameters on the radiation forces are discussed in detail. Comparing with the isotropic particle, the equilibrium status is sensitive to the anisotropic parameters. Moreover, the properties of optical force on a uniaxial anisotropic sphere in single ZOBB trap and zero-order Bessel standing wave trap are compared. The theory and results of this paper are hopeful to provide an effective theoretical basis for the study of optical micromanipulation of biological and anisotropic complex particles by multi-beams.