Ghomashi B, Walker S, Becker A
JILA and Department of Physics, University of Colorado, Boulder, CO, 80309-0440, USA.
Sci Rep. 2023 Aug 8;13(1):12843. doi: 10.1038/s41598-023-39814-y.
Enabling elliptically polarized high-order harmonics overcomes a historical limitation in the generation of this highly nonlinear process in atomic, molecular and optical physics with applications in other branches. Here, we shed new light on a controversy between experimental observations and theoretical predictions on the possibility to generate harmonics with large ellipticity using two bichromatic laser pulses which are linearly polarized in orthogonal directions. Results of numerical calculations confirm the previous experimental data that in short laser pulses even harmonics with large ellipticity can be obtained for the interaction of such cross-polarized laser pulses with atoms initially in a s- or p-state, while odd harmonics have low ellipticity. The amount of the ellipticity can be controlled via the relative carrier-envelope phase of the pulses, their intensity ratio and the duration of the pulses.
实现椭圆偏振高阶谐波克服了原子、分子和光学物理中这一高度非线性过程产生方面的一个历史限制，该过程在其他分支中也有应用。在此，我们为关于使用两个在正交方向上线性偏振的双色激光脉冲产生大椭圆率谐波可能性的实验观测与理论预测之间的争议带来了新的见解。数值计算结果证实了先前的实验数据，即对于最初处于s或p态的原子与这种交叉偏振激光脉冲的相互作用，在短激光脉冲中可以获得具有大椭圆率的偶次谐波，而奇次谐波的椭圆率较低。椭圆率的大小可以通过脉冲的相对载波包络相位、它们的强度比和脉冲持续时间来控制。
