Fluctuation-mediated orbital rotation of microparticles in non-coaxially counter-propagating optical tweezers

Abstract

We have demonstrated in the present report that dielectric microparticles exhibited orbital rotation in the light field of non-coaxially configured two counter-propagating laser beams both in numerical simulations and experiments. A series of computational simulations indicated that when irradiated with two non-coaxially counter-propagating parallel laser beams with same intensity distributions in the absence of thermal (Brownian) motion, a microparticle did not exhibit orbital rotation due to the symmetry of the optical field. However, the computations predicted that a microparticle exhibited one directional orbital rotation in the presence of thermal motion because of the symmetry breaking of the optical force acting on the particle. This spontaneous orbital rotation was experimentally demonstrated for 1-µm dielectric particles in water at room temperature.

Modulation of optical force acting on small particles by using photochemical reaction and its application to control of optical transportation speed

“…However, we have recently demonstrated continuously working microscopic orbital motions with a simple setup. We employed a pair of non-coaxial counter propagating lasers and thermal fluctuation for an orbital motion of a microparticle [10]. In the present study, we modified the transportation speed of microparticles in such orbital motions as well as linear motions by using photochemical reactions.…”