Interaction of forward and backward waves in a Kerr medium

Interaction of forward and backward waves in a nonlinear medium exhibiting a third-order nonlinearity (the Kerr medium) is investigated theoretically. We have analyzed the propagation of two quasi-harmonic waves with different carrier frequencies, such that the phase velocity at one frequency has the same direction as the group velocity, while the phase and the group velocities at the other frequency have opposite directions. Coupling between the waves in a Kerr medium is caused by cross modulation. It is demonstrated that a steady-state biharmonic wave propagating as a single whole can be formed in this situation.