Optical ratchets with discrete cavity solitons
  We propose a setup to observe soliton ratchet effects using discrete cavity solitons in a one-dimensional array of coupled waveguide optical resonators. The net motion of solitons can be generated by an adiabatic shaking of the holding beam with zero average inclination angle. The resulting soliton velocity can be controlled by different parameters of the holding beam. 
Andrey V. Gorbach, Sergey Denisov, and Sergej Flach