We obtain large fractional pulse delays in a Cesium vapor for a probe centered between two absorption resonances in the hyperfine structure. This delay can be tuned by applying pump fields to the absorption lines.
Optically tunable pulse delays in cesium vapor were demonstrated by pumping several D2 transitions and burning holes in the D1 absorption spectrum. A modified sub-Doppler absorption spectroscopy setup was used with counter propagating beams with a Gaussian 7-ns full-width at half-maximum probe pulse is scanned across the D1 absorption spectrum. Probe laser optical delays followed Kramers-Kronig model prediction for Cs D1 without D2 pump laser. Optical control of pulse delay was demonstrated by varying pump intensity. Localized delay effects in agreement with model predictions were observed in the neighborhood of a burnt hole.