Ponderomotive forces on waves in modulated media

Nonlinear interactions of waves via instantaneous cross-phase modulation can be cast in the same way as ponderomotive wave-particle interactions in high-frequency fields. The ponderomotive effect arises when rays of a probe wave scatter off perturbations of the underlying medium produced by a second, modulation wave, much like charged particles scatter off an oscillating electromagnetic field. Parallels with the point-particle dynamics, which itself is subsumed under this theory, lead to new methods of wave manipulation, including asymmetric barriers for light.