Effect of spatial coherence on propagation, tight focusing, and radiation forces of an azimuthally polarized beam

摘要

We report experimental generation of an azimuthally polarized (AP) beam with variable spatial coherence. The effect of spatial coherence on the propagation properties of an AP beam is studied both numerically and experimentally, and our experimental results agree well with the theoretical predictions. The dependence of the intensity distribution of an AP beam focused by a high numerical aperture objective lens on its initial spatial coherence is illustrated numerically, and it is found that we can shape the beam profile of a tightly focused AP beam by varying its initial spatial coherence. Furthermore, the radiation forces on Rayleigh particles induced by a tightly focused AP beam are studied, and we find that the tightly focused AP beam can be used to trap a Rayleigh particle whose refractive index is larger or smaller than that of the ambient by varying its initial spatial coherence. Our results will be useful for particle trapping and material thermal processing.