Phase dependent vectorial current control in symmetric noisy optical ratchets

Abstract

In this work we demonstrate single microparticle transport in a symmetric noisy optical ratchet where each potential is a low power ($<2.5$ mW) three dimensional trap. The optical potentials consist of 20 symmetric optical traps arranged in a one-dimensional lattice produced by a spatial light modulator. The external periodic force of the ratchet system adds to zero over one period (symmetric) and is generated by the motion of a piezo-electric microscope stage. Transport is achieved by adding noise to the potentials by randomly varying the diffracted power into the traps at the same frequency of the external force. We show that the direction and speed of motion (current) is coupled to the phase difference between the noise in the optical potentials and the external periodic force.