用三维时域有限差分法对光镊装置中介质球微粒所受光阱力情况进行模拟。根据Richards-Wolf矢量场衍射积分公式对消球差会聚透镜像空间中电磁场分布的表示，在总场空间中实现了对聚焦光脉冲的模拟。聚焦光脉冲与介质球微粒的相互作用，通过离散傅里叶变换提取出单频成分，利用计算光阱力的麦克斯韦应力张量公式，计算单频激光对介质球的光阱力。聚焦光脉冲的引入可以使一次计算得到多个频率下的计算结果。对相同的聚焦装置下介质球受不同频率入射光的光阱力情况进行了计算。计算结果表明使用线偏振光作光源时，大数值孔径聚焦透镜和短入射波长有利于介质球的横向操纵；沿光轴方向对介质球进行纵向操纵，需要大数值孔径的物镜和与之相适应的入射波长。

Numerical simulation of the optical force exerted on dielectric nanosphere in laser trapping device with three dimensional finite-difference time-domain (FDTD) method is proposed. The focused light pulse is implemented in FDTD total field zone according to Richards-Wolf vectorial diffraction theory. The monochromatic field is extracted from the interacted electromagnetic field between focused light pulse and dielectric nanosphere by discrete Fourier transform, and the results are substituted into Maxwell stress tensor to calculate the optical force. The method is accurated for both simulation of focused light pulse and calculation of optical force because it is based on strict theories. High efficiency can be achieved for using focused light pulse as incident source. The optical force exerted on dielectric nanosphere is calculated when the sphere center is moving in the focal plane and along the axis of the object lens. From the calculation results we can conclude that the high numerical aperture object lens and short wavelength benefit the transverse manipulation of dielectric nanosphere in the focal plane, and high numerical aperture object lens with appropriate wavelength can trap dielectric nanosphere along the axis of the lens.