Electromagnetically induced transparency in a multi-level system of Doppler-broadened Cesium atom*

Doubly dressed electromagnetically induced transparency in a multi-level ladder-type system of Doppler-broadened cesium atom is observed. These doubly-dressed states are established by using a strong coupling laser and a moderate probe laser in a multi- level atomic configuration. The probe laser was locked at the hyperfine transition $|6S_{1/2},F^{\prime\prime}=4\rangle\leftrightarrow |6P_{3/2},F^\prime=4\rangle$ of Cs atom while the coupling laser scanned from $|6P_{3/2},F^\prime\rangle$ levels across the $|8S_ {1/2},F=3\rangle$ and $|8S_{1/2},F=4\rangle$ levels. These two laser beams were counter-propagated and overlapped inside the Doppler-broadened cesium cell under room temperature. Hyperfine levels of $|6P_{3/2},F^\prime\rangle$ serve as a doubly-dressed intermediated states for this ladder-type transitions. The absorption spectra of different probe laser intensity are investigated. Numerical simulation based on solving the steady-state Bloch equations can fit the observed spectrum well.