Creation of rotating spiral structures using interfering Bessel beams for optical manipulation

A simple and effective optical tweezer setup which uses the interference of two counter propagating Bessel beams is proposed and investigated. The potential energy of a Rayleigh particle in the generated interference patterns is numerically evaluated by writing a MATLAB code. A rigorous analytical treatment is also performed for verification the numerical results. The results show that the generated patterns have a spiral structure. It was also found that these spiral patterns and consequently the trapped particles can be rotated about the axis of the patterns by introducing a phase difference between the two beams. The suggested setup is hoped to provide an effective way for guiding particles along the spiral trajectories, making a laser-driven micro- and nanomotor, measuring the torsional properties of biological molecules and separating particle from a liquid mixture according to their mass, size or refractive index.