Fig. 1. Diagrams of experimental details. (a) Schematic diagram of transition between degenerate energy levels in D1 line of ¹³³Cs atom; (b) schematic diagram of experimental equipments

Fig. 2. Normalized transmission spectra of signal light and conjugate light for 4 kinds of transitions between degenerate energy levels at different temperatures. (a) F_g=4→F_e=3; (b) F_g=4→F_e=4; (c) F_g=3→F_e=3; (d) F_g=3→F_e=4

Fig. 3. Zeeman sublevels for 4 kinds of transitions between degenerate energy levels. (a) F_g=4→F_e=3; (b) F_g=4→F_e=4; (c) F_g=3→F_e=3; (d) F_g=3→F_e=4

Fig. 4. Effects of various experimental parameters on gains of signal light and conjugate light in three kinds of transitions between degenerate energy levels. (a) Pump power; (b) temperature of Cs atomic chamber; (c) frequency detuning of pump light

Fig. 5. Schematic diagrams of transitions between different degenerate energy levels after introducing driving light of 852 nm. (a) F_g=4→F_e=3; (b) F_g=4→F_e=4

Fig. 6. Effect of introducing driving light of 852 nm on gain of a pair of DFWM conjugated beams. (a)(c) Gains of DFWM signals versus pump power; (b)(d) normalized transmission spectra at maximum gain