The evolution of the phase of a weak signal wave (ω2) copropagating with a strong gate wave (ω1) in a centrosymmetric medium is studied analytically and numerically for the case when the two waves are involved in a nearly phase-matched third-order process that generates a third wave (ω3=2ω1+ω2). It is shown that the signal wave collects, in addition to the phase shift that is due to the ω2=ω1+ω2−ω1 process, an extra nonlinear phase shift caused by cascading of two third-order nonlinear processes, ω3=2ω1+ω2 and ω2= ω3−2ω1. The attractive feature of this new type of cross-phase modulation is the fact that one can control its magnitude and sign by changing the wave-vector mismatch of the sum-frequency mixing process and the gate intensity.
© 1999 Optical Society of America
S. Saltiel, K. Koynov, K. Kirov, and K. Petrova, "Cross-phase modulation caused by cascading of third-order processes," J. Opt. Soc. Am. B 16, 262-266 (1999)