The controllable amplitude and shape of hyperfine spectra in a ladder-type three-level atomic system

We report experimentally the properties of the hyperfine spectra in [Formula: see text]–[Formula: see text]–[Formula: see text] transitions of [Formula: see text]Rb. When the frequency of the coupling field is fixed between [Formula: see text]–[Formula: see text] transition and the probe scans the [Formula: see text]–[Formula: see text] transitions, two-photon absorption (TPA) and electromagnetically induced transparent (EIT) peaks could be investigated simultaneously, and the amplitude of the peaks can be controlled by changing the temperature of rubidium atomic vapor cell and the probe field power. In particular, the probe field power plays a dual role in controlling the amplitude of the peaks. In the [Formula: see text]–[Formula: see text]–[Formula: see text] transitions with the open intermediate state [Formula: see text], with decrease of the coupling field power, our experimental results show a crossover from a convoluted line-shape to EIT when the probe is weak whereas a transformation from a convoluted line-shape to TPA with an enhanced probe power. Formation of the convoluted line-shape is explained by virtue of the dressed energy-level diagram.