光纤探针型近场光镊光阱力特性研究

基于动量守恒原理,结合麦克斯韦应力张量和三维时域有限差分方法,建立了近场空间内激光光镊对纳米微粒的光阱力计算模型.分析了光纤探针型近场光镊的近场分布以及操作纳米微粒时各轴向光阱力的分布情况,并探讨了光纤探针尖端的捕获尺寸、捕获位置和操作稳定性.结果表明:微粒应处于光纤探针针尖的近场空间内才可实现稳定可靠的纳米操作,不同尺寸的微粒具有不同的捕获效果,且随初始位置的不同微粒的捕获位置亦不同.计算结果为激光近场光镊纳米操作装置的设计和制造提供了理论基础.

Nano-manipulation of Near-field Optical Tweezers Using a Fiber Probe

In order to reveal the near-field distribution of electromagnetic field and the axial distribution of trapping force acting on nano-particles located in near-field optical tweezers,and to explore the trapping size,trapping location and trapping stability,the direct calculations of Maxwell stress tensor were solved numerically by using three-dimensional finite difference time domain method without the limitation of dipole approximation.Calculations show that the particle with radius larger than the aperture is pushed away from the tapered metal-coated fiber probe,while it tends to be trapped in larger effective region as the radius becoming smaller.The near-field optical probe can trap and manipulate a nano-particle with tens of nanometres diameter to different positions with different distance from the probe tip.Results of the calculations are found to be helpful for the design and manifacturing of near-field optical tweezers system.