Double-Λ scheme of the D₂ line of ⁸⁵Rb. The energy level configuration is taken as the following: |1〉 = |5S_1/2, F = 2〉 and |2〉 = |5S_1/2, F = 3〉 are two ground states of the ⁸⁵Rb atoms, and |3〉 = |5P_3/2, F′〉 is the excited state. The hyperfine splitting of the excited state is not resolved compared with our large detuning.