Spin angular momentum and tunable polarization in high-harmonic generation
Spin angular momentum and tunable polarization in high-harmonic generation
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DOI：
10.1038/nphoton.2014.108
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发表时间：
2014-07-01
期刊：
影响因子：
35
通讯作者：
Cohen, Oren
中科院分区：
文献类型：
--
作者：
Fleischer, Avner;Kfir, Ofer;Cohen, Oren
过去研究了能量、动量和轨道角动量守恒在高次谐波产生中的作用。在这里，我们通过实验产生与各向同性介质相互作用的双色椭圆偏振泵浦光束的高次谐波，探索自旋角动量在高次谐波产生中的作用。我们用一个模型定性地解释了许多观察到的复杂选择规则，该模型包括将许多泵浦光子转换为单个光子时的自旋守恒。然而，我们也观察到与该模型的明确偏差，表明椭圆偏振高能光子的发射伴随着额外的激发（辐射或电子）。所提出的结果对于应用也很重要，因为我们的系统可以完全控制谐波的偏振，从圆形偏振到椭圆形偏振再到线性偏振，而不会影响过程的效率。这项工作为高次谐波产生的广泛应用铺平了道路，包括分子和磁性材料的超快圆二色性。
The roles of energy, momentum and orbital angular momentum conservation in high-harmonic generation were studied in the past. Here, we explore the role of spin angular momentum in high-harmonic generation by experimentally generating high harmonics of bichromatic elliptically polarized pump beams that interact with isotropic media. We explain qualitatively many observed intricate selection rules with a model that includes spin conservation in the conversion of many pump photons into a single photon. However, we also observe unequivocal deviations from this model, indicating that emission of an elliptically polarized high-energy photon is accompanied by an additional excitation (radiative or electronic). The presented results are also important for applications, because our system exhibits full control over the polarization of the harmonics, from circular through elliptical to linear polarization, without compromising the efficiency of the process. This work paves the way for a broad range of applications with high-harmonic generation, including ultrafast circular dichroism of molecules and magnetic materials.