Sub-micron scale Brownian swimmer or surfer in one dimensional standing wave optical traps

An optical conveyor belt created by a standing wave can be used to deliver Brownian particles in a controlled way. The dependence of the particle speed on the speed of traveling standing wave is not simple but two basic modes can be distinguished. For very slow standing wave motion the particle is tightly coupled to the potential, i.e. it "surfs along with the potential wave" and therefore it is called the "Brownian surfer". For bigger standing wave velocities the particle behaves like a swimmer afloat on the surface of the ocean and thus it is called the "Brownian swimmer". The mutual speed of the particle and the standing wave is studied experimentally and theoretically.