Dynamical analysis of an optical rocking ratchet: Theory and experiment

TL;DR

This paper provides a comprehensive theoretical and experimental analysis of an optical rocking ratchet system, revealing how particle size influences potential asymmetry and current reversals, with implications for particle separation.

Contribution

It offers the first combined theoretical and experimental study of the dynamics in an optical rocking ratchet, highlighting the role of particle size in potential asymmetry and current reversal mechanisms.

Findings

Particle size affects the asymmetry of the optical potential.

Conditions for current reversals are identified.

Experimental results validate the theoretical analysis.

Abstract

A thorough analysis of the dynamics in a deterministic optical rocking ratchet (introduced in A. V. Arzola et al., Phys. Rev. Lett. 106, 168104 (2011)) and a comparison with experimental results are presented. The studied system consists of a microscopic particle interacting with a periodic and asymmetric light pattern, which is driven away from equilibrium by means of an unbiased time- periodic external force. It is shown that the asymmetry of the effective optical potential depends on the relative size of the particle with respect to the spatial period, and this is analyzed as an effective mechanism for particle fractionation. The necessary conditions to obtain current reversals in the deterministic regime are discussed in detail.