The Study Of Optical Trapping Acting On A Rayleigh Dielectric Sphere

Optical trapping has been an important branch of Modern Optics. Because of the non-touched, low damaged advantages, it has been widely applied to manipulate micron-, nano-object, especially for biological cells.This paper mainly focuses on the study of Rayleigh dielectric spheres. In the second chapter, we investigate the optical trapping effect of high-order Laguerre-Gaussian (LG) beams acting on a dielectric sphere in Rayleigh regime. For LG beams with the azimuthal mode index l=0, it is found that under the same input power, the transverse trapping effect can be enhanced several times with increasing the radial mode index p, compared with that of the Gaussian beam; while its axial trapping effect is exactly the same as that of Gaussian beam. For LG beams with l≠0, we find that the maximal transverse gradient forces increase with the increasing of p and the axial radiation forces reduces slightly.In the third chapter, we discuss behavior of a Rayleigh sphere moving in a fluid, and analyze the displacement and velocity of the particle which is radiated in the field of pulsed Gaussian beam. Finally we demonstrate that only beam with long pulsed duration, it can stable trap the small Rayleigh sphere.In chapter four, we deduce analytical expression of Optical Angular Momentum (OAM) and Poynting vector of the array vortex beam. And we analyze the relation between OAM and number of beamlets, radius of radial ring, topological number. Finally we numerical simulate the dynamic motion of the Rayleigh particle under the radiation of the array vortex beam.In summary, we have investigated the trapping effect of different beams and pulses acting on a Rayleigh dielectric sphere. Our results have significance to experiment observation the trapping of Rayleigh particle. Meanwhile we provide a feasible method in the field of trapping biological cells more efficiently with less power.