球差对光镊中粒子轴向力的影响

Effect of Spherical Aberrations on the Axial Force of Particle in Optical Tweezers

利用几何光学模型,取不同的粒子半径、数值孔径和探测深度,计算光镊中粒子受到的轴向力.从粒子在空间各位置的轴向力及其变化,分析球差对捕获效率的影响.计算结果表明:球差的存在,使得激光没有理想聚焦点,粒子在光镊中的稳定平衡点向负光轴方向位移,并降低了光镊捕获粒子的稳定性.

Axial force exerting on the particle in optical tweezers was calculated with different radii of particles, numeri- cal apertures and detection depths in ray optics model. Through detecting the axial force and its changing versus the spa- tial positions, the effect of spherical aberrations on the efficiency of optical trapping was analyzed. The results of calcula- tion show that, owing to the existing of spherical aberration, the ideal focus of the laser beam is disappear, the stable e- quilibrium point is moved along the negative optical axis direction, and the stability of optical trapping is reduced.