PHOTON-ECHOES AND RELATED 4-WAVE-MIXING SPECTROSCOPIES USING PHASE-LOCKED PULSES

The use of phase-locked pulses in various spectroscopic techniques related to the third-order polarization P(3) is analyzed. Using correlation function expressions for the nonlinear response function, we clarify the interrelationship among several photon echo, pump-probe, and spontaneous light emission techniques, without alluding to any specific model for the material system. By combining phase-locked pulses and heterodyne detection it becomes possible to probe separately the real and imaginary parts of the nonlinear response function. Combining two phase-locked pulse excitation with time-resolved detection of the spontaneous light emission allows direct separation of the Raman and fluorescence contributions.