Photovoltaic versus optical tweezers.

The operation of photovoltaic (PV) tweezers, using the evanescent light-induced PV fields to trap and pattern nano- and micro-meter particles on a LiNbO(3) crystal surface, is discussed. The case of a periodic light pattern is addressed in detail, including the role of particle shape and the modulation index of the light pattern. The use of a single Gaussian light beam is also considered. Illustrative experiments for the two situations are presented. The performance of such PV tweezers in comparison to the best established case of optical tweezers, using optical forces, is considered. Differential features between the two trapping approaches are remarked.