Fig. 1. Energy level diagram of Cs $6{\mathrm{S}}_{1/2}-6{\mathrm{P}}_{3/2}-8{\mathrm{S}}_{1/2}$ for two-color polarization spectroscopy: the circularly polarized 852.3 nm pump laser drives ${\sigma }^{+}$ transitions and induces an anisotropy in the atomic medium, which is detected by a linearly polarized 794.6 nm probe laser between the excited state $6{\mathrm{P}}_{3/2}-8{\mathrm{S}}_{1/2}$ transition.

Fig. 2. Schematic diagram of the experimental setup for two-color polarization spectroscopy. DL: diode laser; OI: optical isolator; HWP: half-wave plate; QWP: quarter-wave plate; PBS: polarizing beam splitting cube; DF: dichroic filter; M: mirror; NDF: neutral density filter; PD: photodiode detector; Cs cell: cesium vapor cell.

Fig. 3. Typical TCPS corresponding to the excited states $6{\mathrm{P}}_{3/2}{\mathrm{F}}^{\prime }=5-8{\mathrm{S}}_{1/2}{\mathrm{F}}^{\prime \prime }=4$ hyperfine transition for the co-propagating configuration.

Fig. 4. Evolution of the (a) magnitude, (b) linewidth, and (c) slope of two-color polarization spectra with increasing 852.3 nm pump power for the counterpropagating and co-propagating experimental configurations between the pump and probe laser beams.

Fig. 5. In the TCPS scanning mode, a theoretical comparison of the EIT atomic coherence effect between the counterpropagating and co-propagating experimental configurations between the pump and probe laser beams in a ladder-type atomic system.

Fig. 6. Experimental comparison of TCPS and DROP/EIT between the counterpropagating and co-propagating experimental configurations between the pump and probe laser beams.

Fig. 7. Evolution of the (a) magnitude, (b) linewidth, and (c) slope of two-color polarization spectra with increasing 794.6 nm probe power for the counterpropagating and co-propagating experimental configurations between the pump and probe laser beams.