Pump-probe approach to multiple scattering of intense laser light from cold atoms

冷原子是具有可控光学性质的单分散无序介质的一个前所未有的例子。这使得冷原子非常适合于研究基本无序诱导的干涉效应，如相干后向散射(CBS)和光的安德森定域化，以及在随机激光器中的应用。如果干扰的多个散射波之间的相干性被打破，则这些干扰效应可以被破坏。对于量子散射体，两种最相关的退相机制是简并原子跃迁的拉曼散射和多光子散射。本项目的目的是进一步发展迄今为止针对两个标量原子的“泵浦-探测”公式。泵浦-探测方法综合了主方程势和图解散射理论方法，是处理稀薄原子介质中饱和原子多次散射的一种很有前途的方法。在本项目中，我们将推广泵浦-探测形式，以便处理矢量原子的多次散射。由此产生的强激光与冷原子的多次散射理论将允许与现有实验进行定量比较。此外，它还将使我们能够对CBS的量子统计签名做出定量预测。

Cold atoms is an unprecedented example of a monodisperse disordered medium with controllable optical properties. This makes cold atoms highly suitable for studies of fundamental disorder-induced interference effects alike coherent backscattering (CBS) and Anderson localization of light, as weIl as for applications in random lasers. These interference effects can be destroyed if coherence between the interfering multiple scattering waves is broken. For quantum scatterers, the two most relevant dephasing mechanisms are Raman scattering on degenerate atomic transitions, on the one hand, and multi-photon scattering, on the other hand.The present project is aimed at a further development of the "pump-probe" formalism which has so far been worked out for two scalar atoms. The pump-probe approach synthesizes the potentials of the master equation and diagrammatic scattering theory approaches, and is hence a promising approach for treating multiple scattering from saturated atoms in a dilute atomic medium. Within the present project, we will generalize the pump-probe formalism in order to treat multiple scattering by vector atoms. The resulting multiple scattering theory of intense laser light from cold atoms will allow a quantitative comparison with existing experiments. Besides, it will enable us to make quantitative predictions concerning the quantum statistical signatures of CBS.