Dynamics of spectral hole burning

A model calculation is presented that describes the features of spectral-hole burning measurements performed under conditions of femtosecond transient excitation and probing. Pump-induced changes in the spectrum of probe transmittance arise not only from changes in level population (hole burning), but also from the presence of pump polarization during the probe, and from perturbations of the decay of the probe polarization. These latter effects give rise to oscillating differential transmittance spectra when the (shorter) probe pulse arrives prior to the peak of the pump noise. Only when the probe pulse follows the bulk of the pump pulse does the level population effect dominate the spectrum, so that one can observe dynamic hole-burning effects without distortion.<>