Dressed states and adiabatic passage for high-intensity nonlinear optics

这个更新方案的目的是扩展我们之前在(去除符号)中关于谐波产生的研究，通过原子多光子共振的相干绝热相互作用来增强谐波产生。我们的特别目标是将相干相互作用的概念转移到高强度的非线性光学中，这些概念在中等激光强度下得到了很好的确立。在我们的工作中，我们应用了修饰态和绝热通过过程。后者提供了对实验参数波动的稳健性，并适用于带宽仍然足够适中的短激光脉冲，以选择性地驱动和利用原子共振。如果驱动光场不超过原子中的库仑场，从而破坏或强烈地改变能级结构，那么通过原子共振的相干绝热控制方法就能很好地工作。另一方面，高效的非线性光学通常需要超快、高强度的激光脉冲。在这种情况下，跃迁的能级结构和光谱形状发生了很大的变化，例如，交流斯塔克位移，很容易达到每太赫兹/平方厘米的激光强度。在这种高强度区域应用共振增强和绝热过程需要新的方法来处理交流电平的变化。正如我们最近在(去掉符号)中展示的那样，即使在高达或超过10TW/cm2的惊人大激光强度下，共振和激光修饰态仍然发挥着相当大的作用。在高强度光-物质相互作用方面，这对应于凯尔德什参数γ接近1。在这个更新方案中，我们将在效率、稳健性和适用性方面改进相干绝热控制方法。我们将研究基于修饰态和绝热通道的替代方法，以提高在高激光强度下驱动的频率转换。此外，我们将研究相干绝热量子动力学如何在更大的强度下朝着更强的光-物质相互作用区域变化，对应于小的凯尔德什参数γ&lt；1。这将为微扰相互作用和强场相互作用之间的共振动力学提供新的基本见解。所提出的研究服务于回答基本的科学问题：通过共振来应用相干绝热量子动力学的极限在哪里？我们能在多大程度上提高激光强度，同时仍然通过修饰态和绝热通道来利用共振和量子相干？当我们施加开始超过原子库仑势的强光场时，这样的过程会发生怎样的变化？哪些控制场景最适合更高强度的应用？有没有办法补偿激光引起的共振位移和展宽？该项目将有助于阐明共振在高强度频率转换中的基本作用(无论是“裸态”还是“穿着激光”态)。

The aim of this renewal proposal is to extend our previous investigations in (sign removed) on harmonic generation, enhanced by coherent-adiabatic interactions via atomic multi-photon resonances. Our particular goal is to transfer concepts of coherent interactions, which are well established at moderate laser intensities, to high-intensity nonlinear optics. In our work we apply dressed states and adiabatic passage processes. The latter offer robustness with regard to fluctuations in experimental parameters and are applicable with short laser pulses of still sufficiently moderate bandwidth to selectively drive and exploit atomic resonances. Coherent-adiabatic control approaches via atomic resonances work well, if the driving laser field does not exceed the Coulomb field in the atom and, hence, destroy or strongly modify the level structure. On the other hand, efficient nonlinear optics usually require ultra-fast, high-intensity laser pulses. In this case, the level structure and spectral shape of transitions change considerably, e.g., by AC Stark shifts, which easily reach many THz per TW/cm² laser intensity. Application of resonance enhancements and adiabatic processes in this high intensity regime requires new approaches to deal with AC level shifts. As we recently demonstrated in (sign removed), resonances and laser-dressed states still play a considerable role even at surprisingly large laser intensities, up to or beyond 10 TW/cm². In terms of high intensity light-matter interaction, this corresponds to a Keldysh parameter γ approaching unity. In this renewal proposal we will refine the coherent-adiabatic control approaches with regard to efficiency, robustness, and applicability. We will investigate alternative approaches based on dressed states and adiabatic passage to enhance frequency conversion, driven at high laser intensity. Moreover, we will study how coherent-adiabatic quantum dynamics change for even larger intensities proceeding towards the regime of stronger light-matter interaction, corresponding to small Keldysh parameter γ<1. This will yield new fundamental insight in the dynamics of resonances in the transition between perturbative interaction and the strong field regime.The proposed investigations serve to answer the basic scientific questions: Where are the limits for applications of coherent-adiabatic quantum dynamics via resonances? How far can we increase the laser intensities and still exploit resonances and quantum coherences via dressed states and adiabatic passage? How do such processes change when we apply intense light fields, which start to exceed the atomic Coulomb potential? Which control scenarios are most appropriate for applications at higher intensities? Are there ways to compensate for laser-induced shifts and broadenings of resonances? The project will serve to clarify the fundamental role of resonances (no matter whether “bare” or “laser-dressed” states) in frequency conversion at high intensities.