An easier way to improve the trapping performance of optical tweezers by donut-shaped beam

In optical tweezers, it can be comprehended that the larger the inclination angle between the condensed laser beam and the optical axis contributes more to axial trapping force, while the central part of laser beam with smaller inclination angle contributes more transverse trapping force. Therefore donut-shaped beam is used to improve the problem of lessaxial trapping for common optical tweezers. Some research reports have shown that the efficiency of a trapping force can be enhanced by using a donut-shaped beam. In this paper we present the dependence of the axial and the transverse components of a trapping force on the configuration of a focused donut-shaped beam. The simulation result will provide a simple and easy guide for optical tweezers users to adjust the configuration of a focused donut-shaped beam for optimal trapping performance.