each of the involved fine states describe well the experimental results, which allows us to use the model to make further predictions about the behavior of the system. Also, we show that we can tune the group delay over a wide range of values by simply varying the temperature of the vapor cell. While this method is very simple, it is rather slow. As an alternative ap- proach, one can apply a separate, strong saturating pulse near one of the resonance lines to optically pump atoms out of the ground state and thereby rapidly ( ∼ 100’s of ns) vary the group index [21]. Furthermore, this atomic-vapor-based scheme can be readily converted to a chip-based geometry [26]. By simply increasing the number of passes that the laser beam makes through the cell, one can either shrink the size of the required vapor cell to obtain a fixed group delay, or increase the total delay for a fixed cell length. One can also use different atomic species to obtain slow light centered on different wavelengths. Such a tunable, broadband slow light medium could be useful for developing more sensitive interferometers [27], variable-depth OCT systems with no moving parts [28], optical precursor experiments, or for quantum light-matter interfaces [29]. We gratefully acknowledge the financial support of the DSO Slow Light program and the Air Force Research Laboratory under contract FA8650-09-C-7932. Also, the authors would like to thank Warren Warren for the use of his lab in carrying out the ultrashort pulse experiments. A. Appendix A: Origin of pulse broadening In general, a pulse with a spectrum located between a pair of resonances will experience broadening due to the combined effects of dispersion and absorption as it propagates. De- pending on the parameters involved, limiting cases exist in which this broadening is almost completely determined by either frequency-dependent absorptive or dispersive effects. For a pair of Lorentzian absorbing lines, as described in Eq. 1, and a Gaussian pulse envelope, we analytically evaluate the relative importance of these two effects. We can calculate separately 13