ab-initio description of optical nonlinearities in femtosecond filaments

飞秒细丝是光和自由电荷的自组织串。这些细丝中的电场强度接近于原子场的强度，因此，激光诱导和高次谐波的产生是非线性光学中最极端的现象之一，在空间和时间域中同时存在着大量的效应。虽然数值模拟是相当先进的，最近，普遍接受的图片bepaly在线网投受到挑战的实验报告表明，以前低估的影响，导致高阶electronicnonlinearities可能推翻等离子体效应。虽然这一理论引起了生动的讨论，一个严格的理论理解去所有的方式回到量子力学的根源，即，薛定谔方程仍然是一个悬而未决的问题。在此，我们提出了一套高次谐波在非线性光学中的作用的理论测试。这些测试从最简单的氢原子或氦原子开始，使用非微扰技术。对于更复杂和实验更相关的场景，我们计划使用含时密度泛函理论来计算诱导偶极矩。这种严格的理论研究似乎是唯一的方法来决定我们是否真的有一个新的范式在非线性光学或旧图片的等离子体效应平衡克尔效应实际上占上风。

Femtosecond filaments are self-organized strings of light and free electric charges. The electric field strength in these filaments comes closeto the atomic field strength.Therefore, laser filamentation, together with high-harmonic generation, is oneof the most extreme scenarios in nonlinear optics, with a largenumber of effects acting simultaneously in the spatial as well as inthe temporal domain. While numerical modeling is quite advanced,recently, the commonly accepted picture of filamentation has beenchallenged by experimental reports that indicate a previouslyunderestimated effect resulting from higher-order electronicnonlinearities which may overrule plasma effects. While this reporthas given rise to vivid discussions, a rigorous theoreticalunderstanding going all the way back to the quantum mechanicalroots, i.e., the Schr\"odinger Equation is still outstanding. Herewe propose a suite of theoretical tests for the role of high-orderharmonics in nonlinear optics. These tests start with the simplestcase of atomic hydrogen or helium, using non-perturbativetechniques. For more complex and experimentally more relevantscenarios, we plan to use time-dependent density functional theoryto calculate the induced dipole moment. Such rigorous theoreticalinvestigations appear to be the only way to decide whether we reallyhave a new paradigm in Nonlinear Optics or whether old pictures ofplasma effects balancing Kerr effects actually prevail.