arXiv:1001.2359 · Physical Review A
Light pulse in Λ -type cold-atom gases
Ran Wei, Bo Zhao, Youjin Deng, Shuai Chen, Zeng‐Bing Chen, Jian-Wei Pan
Abstract
We investigate the behavior of the light pulse in $\ensuremath{\Lambda}$-type cold-atom gases with two counter-propagating control lights with equal strength by directly simulating the dynamic equations and exploring the dispersion relation. Our analysis shows that, depending on the length ${L}_{0}$ of the stored wave packet and the decay rate $\ensuremath{\gamma}$ of ground-spin coherence, the recreated light can behave differently. For long ${L}_{0}$ and/or large $\ensuremath{\gamma}$, a stationary light pulse is produced, while two propagating light pulses appear for short ${L}_{0}$ and/or small $\ensuremath{\gamma}$. In the $\ensuremath{\gamma}\ensuremath{\rightarrow}0$ limit, the light always splits into two propagating pulses for a sufficiently long time. This scenario agrees with a recent experiment [Y.-W. Lin et al., Phys. Rev. Lett. 102, 213601 (2009)] where two propagating light pulses are generated in laser-cooled cold-atom ensembles.