We discuss the non-dipole effect in high-order harmonic generation from atoms driving by a linearly polarized vortex beam. Different from the selection rule under the dipole approximation, where only odd high harmonics are allowed, both even and odd harmonics are generated in the vortex beam. Moreover, the polarization states of the harmonics are modulated. Elliptically polarized high harmonics can be directly generated with a linearly polarized vortex beam. We show that these non-dipole effects arise from the orbital angular momentum and spin angular momentum of the vortex beam.

中文翻译：

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涡旋高次谐波产生中的非偶极效应

我们讨论了由线性偏振涡旋束驱动的原子在高次谐波产生中的非偶极效应。与偶极近似下的选择规则不同，在偶极近似下，仅允许奇次高次谐波，而在涡流束中均会产生偶次和奇次谐波。此外，谐波的极化状态被调制。椭圆偏振的高次谐波可以通过线性偏振的涡旋光束直接产生。我们证明了这些非偶极效应是由涡旋光束的轨道角动量和自旋角动量引起的。