Trapping two types of particles using a focused partially coherent modified Bessel-Gaussian beam

摘要

Using the extended Huygens-Fresnel principle and Rayleigh scattering regime, the analytical expressions for the intensity and radiation forces of a focused partially coherent modified Bessel-Gaussian (MBG) beam have been derived, and used to study the optical trapping effect of the focused partially coherent MBG beams acting on dielectric sphere with different refractive indices. The results show that the focused partially coherent MBG beam with m=0 cannot capture the low index of refraction particles, but can trap the high index of refraction particles. The focused partially coherent MBG beam with m = 1 can trap the high index of refraction particles to a ring on the focal plane, and simultaneously capture the low index of refraction particles to z-axis. When the topological charge m increases, the radiation force decreases while the transverse trapping range increases for low and high index of refractive particles. Besides, larger the value of the spectral degree of coherence xi is, the easier the two types of particles are trapped by the focused partially coherent MBG beam. Trapping stability is also analysed. The obtained results are useful for analysing the trapping efficiency of focused partially coherent MBG beam applied in micromanipulation and biotechnology.