arXiv:1107.5432v1 [quant-ph] 27 Jul 2011 1 Controllable ultra-broadband slow light in a warm Rubidium vapor Rui Zhang, 1$_{,}$3 Joel A. Greenberg, 1$_{,}$3$_{,}$ ∗ Martin C. Fischer, 2 and Daniel J. Gauthier 1 2 Department of Chemistry and the Fitzpatrick Institute for Photonics, Duke University, Durham, NC 27708, USA 3 The first two authors contributed equally to this work ∗ Corresponding author: jag27@phy.duke.edu 1 Department of Physics and the Fitzpatrick Institute for Photonics, Duke University, Durham, NC 27708, USA We study ultra-broadband slow light in a warm Rubidium vapor cell. By working between the D1 and D2 transitions, we find a several-nm window centered at 788.4 nm in which the group index is highly uniform and the absorption is small ( < 1%). We demonstrate that we can control the group delay by varying the temperature of the cell, and observe a tunable fractional delay of 18 for pulses as short as 250 fs (6.9 nm bandwidth) with a fractional broadening of only 0.65 and a power leakage of 55%. We find that a simple theoretical model is in excellent agreement with the experimental results. Using this model, we discuss the impact of the pulse’s spectral characteristics on the distortion it incurs during propagation through the vapor. c ○ 2018 Optical Society of America OCIS codes: 060.1155, 190.0190, 020.0020