Generation of circularly polarized high-order harmonics by two-color coplanar field mixing
Generation of circularly polarized high-order harmonics by two-color coplanar field mixing
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DOI：
10.1103/physreva.61.063403
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发表时间：
2000-06-01
影响因子：
2.9
通讯作者：
Kopold, R
中科院分区：
文献类型：
--
作者：
Milosevic, DB;Becker, W;Kopold, R
研究了双色激光场产生圆偏振高次谐波的引脚有效方法，该双色激光场的两个频率为ω和2 ω的分量在同一平面内圆偏振，但旋转方向相反。这种驱动场结构产生的强谐波已经在先前的实验中得到证实。借助于半经典三阶模型和鞍点分析，阐明了这种情况下谐波产生的机理，建立了谐波响应的平台结构及其截止点。研究了谐波产率和谐波极化对驱动场不完全圆极化的敏感性。讨论了截止频率和谐波效率随驱动场两分量强度比的优化问题。确定了产生特定谐波的电子轨迹。与线极化驱动场的情况不同，它们具有非零启动速度。通过与两分量同向旋转的驱动场形态的比较，进一步阐明了强谐波发射的机理。根据（未知的）反旋转极化双色场的饱和强度，该方案可能具有实际意义，不仅因为所产生的谐波是圆偏振的，而且还因为它们的产生效率。
Pin efficient method is investigated for the generation of,circularly polarized high-order harmonics by a bichromatic laser field whose two components with frequencies omega and 2 omega are circularly polarized in the same plane, but rotate in opposite directions. The generation of intense harmonics by such a driving-field configuration was already confirmed by a previous experiment. With the help of both a semiclassical three-step model as well as a saddle-point analysis, the mechanism of harmonic generation in this case is elucidated and the plateau structure of the harmonic response and their cutoffs are established. The sensitivity of the harmonic yield and the polarization of the harmonics to imperfect circular polarization of the driving fields are investigated. Optimization of both the cutoff frequency and the harmonic efficiency with respect to the intensity ratio of the two components of the driving field is discussed. The electron trajectories responsible for the emission of particular harmonics are identified. Unlike the case of a linearly polarized driving field, they have a nonzero start velocity. By comparison with the driving-field configuration where the two components rotate in the same direction, the mechanism of the intense harmonic emission is further clarified. Depending on the (unknown) saturation intensity for the bichromatic field with counter-rotating polarizations, this scheme might be of practical interest not only because of the circular polarization of the produced harmonics, but also because of their production efficiency.