对向传播光场激发下二能级原子系综斑图形成不稳定性分析
Analysis of pattern forming instabilities in an ensemble of two-level atoms optically excited by counter-propagating fields
摘要：
本文研究了在激光驱动下，带平面反馈镜的冷二能级原子云中的斑图形成不稳定性的各种模型。重点是在衍射厚介质中的非线性传播和反馈的边界条件的联合处理。讨论了波长尺度上纯横向透射光栅和反射光栅的组合存在。不同的截断水平的傅立叶展开的介电极化率在这些光栅进行了讨论，并与文献。提出了一种计算存在吸收时均匀态的精确解的方法。讨论了反向传输光束不稳定性与反馈不稳定性之间的关系。在最佳条件下，反馈将阈值降低到原来的两倍。包络曲线，约束所有可能的阈值曲线变化的镜距离计算。结果比较以及所观察到的长度尺度和阈值条件的实验结果。它澄清了衍射薄介质的假设是合理的。
英文摘要：
We explore various models for the pattern forming instability in a laser-driven cloud of cold two-level atoms with a plane feedback mirror. Focus is on the combined treatment of nonlinear propagation in a diffractively thick medium and the boundary condition given by feedback. The combined presence of purely transverse transmission gratings and reflection gratings on wavelength scale is addressed. Different truncation levels of the Fourier expansion of the dielectric susceptibility in terms of these gratings are discussed and compared to literature. A formalism to calculate the exact solution for the homogenous state in presence of absorption is presented. The relationship between the counterpropagating beam instability and the feedback instability is discussed. Feedback reduces the threshold by a factor of two under optimal conditions. Envelope curves which bound all possible threshold curves for varying mirror distances are calculated. The results are comparing well to experimental results regarding the observed length scales and threshold conditions. It is clarified where the assumption of a diffractively thin medium is justified.
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