A study of pulse shape in electromagnetically induced transparency based slow light

Slow light of four different pulses are demonstrated and analyzed in cesium vapor based on electromagnetically induced transparency. Each pulse, generated with an identical temporal width, experiences very different slow light effects due to its temporal and spectral distributions simultaneously. Aiming at the applications such as timing, instead of communication, we obtained two optimized ones among the four different shaped pulses. Firstly, the single-exponential pulse is more appropriate to maximize the time delay than other three pulses; secondly, the cosine pulse shows advantage to minimize the distortion (broadening) of the slowed pulse. Finally, using optical filter model, we present a convenient simulation method in theory; moreover, the theoretical results show excellent agreement with experiments.