Experimental observation of pump-probe spectra of caesium D₂ line with a vapour cell

Pump-probe spectra of cesium (Cs) D₂ line are experimentally investigated in a Cs atomic vapor cell with co-propagating orthogonal linearly-polarized pump and probe laser beams. Absorption-reduction dips duo to electromagnetically induced transparency (EIT) in multi-\Lambda-type Zeeman sublevels of 6 S_1/2 F=3 – 6 P_3/2 F’=2 hyperfine transition and absorption-enhanced peaks due to electromagnetically induced absorption (EIA) in 6 S_1/2 F=4 – 6 P_3/2 F’=5 hyperfine transition are demonstrated. With detuned pump beam abnormal sign-reversed signals inside the EIT dip and the EIA peak are clearly observed.