Breaking the Action-Reaction Principle of Light Interactions Under a Stroboscopic Nonlinearity

The action-reaction principle is proven violated in multitudes of physical systems under certain circumstances, but such a violation is rarely reported in the interplay (via nonlinearity) of optical fields, particularly in experiment. Here a realistic optical platform is demonstrated for realizing light interactions that break the law of action-reaction. Under a stroboscopic nonlinearity where self-focusing and -defocusing effects come to play the role periodically, two optical beams are judiciously trimmed temporally to experience the two inverted nonlinear effects. During their interaction, they show deflections toward the same direction. The underlying physics is in sharp contrast to that in the attraction/repulsion or diametric drive behavior commonly seen in all previous experiments. In addition, the wave dynamics introduce an extra feature that has no counterpart in particle interactions breaking the action-reaction principle. The counterintuitive interplay realized here in optics may bring about new ways for light manipulation.