相干和非相干合成光束对金属瑞利粒子的光学俘获

研究了两光束的合成方式(相干和非相干合成)对俘获金属瑞利粒子的辐射力和稳定性的影响,着重研究了辐射力与合成方式、离轴距离、相干参数和粒子半径的关系.结果表明,不同合成方式下,离轴距离和相干参数都分别存在临界值d_c和α_c,在0d_c或α>α_c时,焦面处光强呈中心凹陷分布,此时横向梯度力不能作为回复力俘获金属瑞利粒子.在0<d≤d_c时,与非相干合成光束比较,相干合成光束在焦面处光强、辐射力、俘获刚性和纵向俘获范围更大.因此,适当选择合成方式,较小离轴距离和较低相干参数可有利于合成光束对金属瑞利粒子的俘获.

Optical trapping of metallic Rayleigh particles by using coherently and incoherently combined beams

The effect of two beam combination schemes,i.e.combination of coherent and incoherent beam,on the radiation force and stability in trapping metallic Rayleigh particles is studied,where the dependences of the radiation force on beam combination scheme, off-axis distance,coherence parameter and particle radius are stressed and illustrated by numerical examples.It is shown that there exist critical values d_c andα_c for different combination schemes.For 0 < d ^ dc or 0 < a ^ qc the Gaussian-like intensity profile takes place in the geometrical focal plane,so that the transverse gradient force can act as a restoration force to provide stable equilibrium point.For d > do,c orσo >σo,c the transverse gradient force can not trap metallic Rayleigh particles.For 0 < d≤dc the intensity, the radiation force,the trapping stiffness,and the longitudinal trapping range of coherently combined beam are larger than those of incoherently combined beams.Therefore,a suitable choice of combination scheme,smaller off-axis distance and coherence parameter is beneficial to trapping metallic Rayleigh particles in the use of combined beams.