Comparative study of optical levitation traps: focused Bessel beam versus Gaussian beams

In optical levitation traps, a light beam propagating upward is focused with a relatively low numerical aperture (NA), producing a large scattering force along the propagation direction, which is balanced by the effective weight of a particle. Here, we present a detailed study of four levitation traps obtained when the trapping beam is a fundamental Gaussian mode focused with different NA, in comparison with a levitation trap obtained with a zero-order Bessel beam focused through a lens with NA = 0.40. A theoretical analysis for the optical field and trapping forces along the lateral and axial directions is presented for all the traps and contrasted with experimental results. We show that the focused Bessel trap offers highly superior capabilities for manipulation of individual glass beads in three dimensions, along with other advantages in comparison with standard optical tweezers, such as an extended working distance, larger field of view, and lower spherical aberration. (C) 2016 Optical Society of America.