Experimental demonstration of novel optical Brownian ratchet by controllable phase profile of light

Abstract

Brownian ratchet has emerged as a promising tool for understanding motion mechanism of molecules and proteins, and dynamically manipulating particles in non-equilibrium thermodynamics state. Here, we propose and experimentally demonstrate a new type of optical Brownian ratchets, which is generated by using controllable phase profiles in holographic optical trapping system. The potential energy profiles are dynamically switched in on-off mode, controlled by Labview software. Experimental results reveal that not only high speed but also large step distance can be easily achieved in Brownian ratchet, in which the average velocity of forward motion is about 28 μm/s and step distance is about 42 μm. More importantly, its motion path, step distance and velocity can be easily changed by manipulating its holograms, which exhibits high flexibility, easy control and excellent capability. This technique provides new opportunities for exploring non-equilibrium dynamics at the nanoscale level, and developing novel nanoparticle manipulation.