Stimulated effects in interferometric four-wave mixing experiments

Summary form only given. Nonlinear techniques using broadband light have been developed and applied for studying dephasing processes, population and orientational dynamics of molecules. These techniques are based on the fact that in wave-mixing processes one may have the time resolution determined by the laser coherence time instead of the laser pulse duration. One limiting factor of the measurement sensitivity is a constant signal (pedestal), which is present even when the delay time between the exciting broadband beams is substantially longer than their coherence time and relaxation time under study. A technique has been developed, which uses not "white" detection, but spectral filtering in field-correlated four-wave mixing, the so called interferometric four-wave mixing (IFWM), which gives a signal that reveals oscillatory modulation, enabling us to discriminate it more easily from the pedestal. The technique allows to determine rather precisely the frequency of a molecular vibration and its dephasing time, as well as to study damped molecular rotations in liquids. We report the first measurements of population relaxation rates affected by stimulated emission in the presence of the pump field applying the IFWM technique.