Generalized phase-matching conditions for high harmonics: The role of field-gradient forces
Generalized phase-matching conditions for high harmonics: The role of field-gradient forces
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DOI：
10.1103/physreva.55.3204
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发表时间：
1997-04-01
影响因子：
2.9
通讯作者：
Lewenstein, M
中科院分区：
文献类型：
--
作者：
Balcou, P;Salieres, P;Lewenstein, M
我们提出了一种方法来描述激光驱动原子在非微扰状态下发射的高次谐波的相位匹配，在这种情况下，原子的响应表现出与强度有关的本征相位。我们证明了传统的涉及波矢守恒的位相匹配条件应该考虑到该原子相的梯度来修正。我们研究了各种聚焦几何结构，并解释了Salieres等人的数值结果。[物理。莱特牧师。74,3776(1995)]。在两步模型的框架下，我们证明了强度相关相的梯度可以看作是电子在连续介质中由于场梯度力(特别是有质动力)加速而获得的正则动量。
We present an approach to describe the phase matching of high harmonics emitted by laser driven atoms in a nonperturbative regime, for which the atomic response displays an intrinsic intensity-dependent phase. We show that the traditional phase-matching conditions involving conservation of wave vectors should be modified by taking into account the gradient of this atomic phase. We investigate various focusing geometries and interpret the numerical results of Salieres et al. [Phys. Rev. Lett. 74, 3776 (1995)]. Within the framework of the two-step model, we demonstrate that the gradient of the intensity-dependent phase can be considered as the canonical momentum gained by the electron in the continuum due to acceleration by field-gradient forces, including in particular the ponderomotive force.