Observation of nonstationary effects in saturation spectroscopy

We have studied the nonstationary effects in saturated absorption spectroscopy of the 87Rb D2 line. Varying the size of the σ+ polarized pump laser beam, we observed saturated absorption spectra for the σ± polarized probe beam. For equal polarizations of the pump and probe beams, we found that the resonance signal for the Fg = 1 → Fe = 2 line, and the crossover lines between Fg = 1 → Fe = 2 and Fg = 1 → Fe = 1 (and 0) lines increased to a greater extent than the others. This observation can be understood from the calculated time evolution of the populations of the ground-state sublevels by means of a rate equation model. We also compared experimental data for other conditions with the calculated results. We found good agreement between the calculated results and the data.