时域有限差分法数值仿真单光镊中微球受到的光阱力

FDTD numerical simulation of the trapping force of microsphere in single optical tweezers

本文采用三维时域有限差分法(FDTD)和Maxwell应力张量法建立了单光镊在焦点附近俘获球形微粒的光阱力模型,采用基于球矢量波函数(VSWF)的五阶高斯光源作为仿真光源,得到了准确的光场传播.讨论了光源的波长、束腰、偏振态和微球的半径、折射率对光阱力的影响,分析了在单光镊俘获微球时,邻近微球对光阱力的影响.特别研究了光源的偏振态对微球所受光阱力的作用效果,仿真结果表明圆偏振光比线偏振光对微球的俘获力更大;被光镊稳定俘获的微球,会受到邻近微球干扰,失去平衡状态,改变光源的偏振态可以改变微球的受力状态.

In this paper the model of trapping force on microsphere near focus in single optical tweezers is built by three dimensional finite-difference time-domain （FDTD） and Maxwell stress tensor methods. Fifth order Gaussian beam based on spherical vector wave function （ VSWF） is adopted as simulation light source; the correct light field transmission is obtained. The influences of the wavelength,waist and polarization of light sources,the radius and refractive index of the microsphere on the optical trapping force are discussed. The influence of nearby microsphere and beam polarization on the trapping force of the trapped microsphere in single optical tweezers is analyzed. The effect of beam polarization working on the trapping force of the trapped microsphere is specially analyzed. As results of simulation,the trapping force acting on the microsphere by the circularly polarized beam is larger than that by the linearly polarized beam. The stability of the trapped microsphere in single optical tweezers will be disturbed by the nearby microsphere and lose its balance. Varying the beam polarization will lead to the change of the trapping force of the trapped microsphere.