Fig. 1. D1 line energy-level diagram of ⁸⁵Rb.

Fig. 2. Experimental setup. DL1 and DL2, diode lasers; PBS, polarizing beam splitter; PD, photodetector; LIA, lock-in amplifier.

Fig. 3. Experimental results for the transmission intensity of the weak probe beam (black solid line) and the FWM signal with narrow linewidth (red solid line) as a function of Δ₁: (a) Δ₂ = 0; (b) Δ₂ = 350 MHz. (Note that in order to see the details clearly, the spectral intensity in Fig. (b) is the result of magnification to 2.5 times the actual situation.)

Fig. 4. Experimental results (red star) and theoretical fitting (black solid line) for the FWM signal. The coupling field intensity I₂ = 1.97 mW and the control field intensity I₃ = 7.4 mW are used in the experiment. The parameters used in the theoretical simulation are , , , .

Fig. 5. (a) FWM (solid line) and SRS (dotted line), and (b) corresponding resonant velocities (solid line) and (dotted line) as a function of when (black), 2.5(red), 4.0(blue).

Fig. 6. (a) FWM (solid line) and SRS (dotted line), and (b) corresponding resonant velocities (solid line) and (dotted line) as a function of when 50.7 (black), 101.4(red), 202.8(blue).