We investigate the high-order harmonic generation (HHG) of the helium atom at the various intensity ratios of the counter-rotating two-color circularly polarized laser fields. The results show that the cutoff energy of the harmonic spectra can be affected by changing the intensity ratios. By comparing the results from different intensity ratios, we find that the distances the electrons travel are short when the intensity ratio is increased. The dependence of the cutoff position in the HHG on the intensity ratios usually results from the classical trajectories of the electrons. As the intensity ratio increases, the electrons cannot be accelerated and it will gain less energy. As a result, the harmonic spectra are cut off at the lower energy. We compare the quantum and classical trajectories results to illustrate the reasons of the cut off dependence.

中文翻译：

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两个驱动激光场的强度比对高次谐波截止的影响

我们研究了在反向旋转的双色圆偏振激光场的各种强度比下氦原子的高次谐波生成 (HHG)。结果表明，改变强度比可以影响谐波光谱的截止能量。通过比较不同强度比的结果，我们发现当强度比增加时，电子行进的距离较短。HHG 中截止位置对强度比的依赖性通常来自电子的经典轨迹。随着强度比的增加，电子不能被加速，它获得的能量就会减少。结果，谐波光谱在较低能量处被截止。