Polarization spectroscopy for the 85Rb D1 line in a strong pump field

We present polarization spectroscopy for the D1 transition line of 85Rb atoms in the strong pump region. When the intensity of the pump beam was increased, the signal for the transition ∣ 5S1/2, Fg = 2〉 → ∣5P1/2, Fe = 3〉 displayed a double structure in the dispersive signal whereas the other signals displayed no significant variation other than power broadening. Calculation of the spectral lineshape by using the rate equations demonstrated that the double structure was due to the relatively large signal for the ground state ∣5S1/2, Fg = 2,mg = 2〉 due to optical pumping and the large transition strength.