We numerically calculate the transient-four-wave-mixing (TFWM) response in systems that exhibit either a resonance frequency or a dephasing rate that depends on the level of excitation, which can occur in semiconductors or a dense atomic vapor. These effects change the intensity dependence of the TFWM signal, causing it to display noncubic behavior for significantly lower pulse areas and even a reduction in signal intensity for increasing pulse area. They also qualitatively change both the temporal behavior and spectrum of the TFWM signal in ways that cannot adequately be described in perturbation theory. For time-integrated TFWM, the saturation behavior is also found to depend on the delay between pulses. For comparison, the effects of local fields are also calculated as they produce similar effects. These results can help provide discrimination among the various phenomena.
© 2003 Optical Society of America
(300.6290) Spectroscopy : Spectroscopy, four-wave mixing
(320.7130) Ultrafast optics : Ultrafast processes in condensed matter, including semiconductors
(320.7150) Ultrafast optics : Ultrafast spectroscopy
J. M. Shacklette and S. T. Cundiff, "Nonperturbative transient four-wave-mixing line shapes due to excitation-induced shift and excitation-induced dephasing," J. Opt. Soc. Am. B 20, 764-769 (2003)