Single-laser-beam trapping and manipulation of microspheres as a model for biological cells

We used a dielectric microsphere model which is based on geometrical optics to describe the generation of trapping force by a single laser beam. Our results show that the microsphere can be trapped in some cases. For a typical microsphere, which has a 10 microns diameter, the trapping point is about 2 microns below the focusing point of the laser, and the trapping range is about 4 microns. The transverse trapping range is about 16 microns. And we find, that if we use suitable TEM mode of the laser beam, we can raise the trapping force for several times. This model can also be extended to biological cells.