Advances in multi-photon processes and spectroscopy
WHAT ROLE CAN FOUR-WAVE MIXING TECHNIQUES PLAY IN COHERENT CONTROL?
Vadim V. Lozovoy, Emily J. Brown, Igor Pastirk, Bruna Irene Grimberg, Marcos M. Dantus
Abstract
The role of four-wave mixing (FWM) techniques in coherent control is considered from the point of view of some of the most important developments in this field over the past years, namely multiphoton excitation, pump-dump methods, interference between coherent pulses, chirped laser pulses, and optimal control. FWM techniques provide a powerful platform for combining coherently multiple laser pulses. We explore the effectiveness of these techniques in controlling chemical reactions. The phase relationship between the pulses is maintained by detecting the signal in a phase-matching direction. The results presented show control over the observed dynamics from ground and excited state populations. The FWM signal results from the polarization of the sample following three different electric field interactions. The virtual echo sequence is achieved by the interactions of the sample with three consecutive electric fields characterized by exp[i(kx-w t)], exp[-i(kx-w t)] and exp[i(kx-w t)]. This sequence allows control over the observed ground or excited state dynamics. With the photon echo pulse sequence, characterized by interactions with exp[-i(kx-w t)], exp[i(kx-w t)], and exp[i(kx-w t)], we find that control of ground and excited state populations is not achieved.