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

冷原子是一种具有可控光学性质的单分散无序介质。这使得冷原子非常适合于研究基本无序诱导的干涉效应，如光的相干背散射（CBS）和安德森局域化，以及在随机激光器中的应用。如果干涉的多次散射波之间的相干性被破坏，这些干涉效应可以被破坏。对于量子散射体，两个最相关的退相机制是简并原子跃迁的拉曼散射，一方面，和多光子散射，另一方面，本项目旨在进一步发展的“泵浦-探测”的形式主义，迄今为止已经制定了两个标量原子。泵浦-探测方法综合了主方程和图解散射理论方法的势函数，是一种很有前途的处理饱和原子在稀原子介质中多次散射的方法。在本项目中，我们将推广泵探测形式主义，以处理多重散射的矢量原子。由此产生的强激光从冷原子的多重散射理论将允许与现有的实验进行定量比较。此外，它将使我们能够对CBS的量子统计特征进行定量预测。

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.