Figure 3

Experimental absorption spectra S(ω − ω₂₁) and S(ω − ω₃₁) at frequencies (a) ω₂₁ = 1.56 eV and (b) ω₃₁ = 1.59 eV of a probe pulse of intensity I_pr = 3.0 × 10⁸ W/cm², transmitted through an ensemble of Rb atoms interacting with a fixed-delay (440 fs) control pulse of varying intensity. Results lined out by the vertical dashed lines in (a) and (b) correspond to the experimental absorption spectrum that shown in (e). Panels (c) and (d) show the amplitude and phase parameters extracted from the time-delay-dependent absorption spectra of varying control-pulse intensities, in which the vertical dashed lines show these parameters that used to generate the simulated result in (e). Results in (e) show the experimental and DCM-fitted absorption spectra with a fixed control-pulse intensity of I_co = 2.13 × 10¹⁰ W/cm², and the horizontal dashed line indicates the zero.