Zhavoronkov Nickolai, Ivanov Mikhail
Opt Lett. 2017 Nov 15;42(22):4720-4723. doi: 10.1364/OL.42.004720.
Attosecond (1 as=10 s) pulses produced through high harmonic generation (HHG) are a basis for studies of electron dynamics during light-matter interaction on an electron's natural time scale. Extensively exploited HHG technology has, however, a few unsolved problems, where producing of circularly polarized or chiral attosecond pulses belongs to them. We have demonstrated experimentally a way to control the ellipticity of attosecond pulse trains produced via HHG in two-color, bi-circular laser fields. We show that the combination of a nonlinear medium position and the intensities of the two-color driving laser fields create an effective helicity-dependent filter. Based on this approach, we report generation of chiral spectra providing potential to produce attosecond pulses with polarization tuned from the rotating, but linear to highly elliptic, with ellipticity as much as ϵ=0.75. This new way to create a chiral-sensitive element offers a simple and practical knob to control polarization for a combined harmonics field in a smooth and predictable manner.
通过高次谐波产生（HHG）产生的阿秒脉冲（1 as = 10⁻¹⁸ s）是在电子自然时间尺度上研究光与物质相互作用期间电子动力学的基础。然而，广泛应用的高次谐波产生技术存在一些尚未解决的问题，产生圆偏振或手性阿秒脉冲就属于这些问题。我们通过实验证明了一种在双色双圆激光场中控制通过高次谐波产生的阿秒脉冲序列椭圆率的方法。我们表明，非线性介质位置与双色驱动激光场强度的组合创建了一个有效的螺旋度依赖滤波器。基于此方法，我们报告了手性光谱的产生，该光谱具有产生偏振从旋转但线性到高度椭圆变化（椭圆率高达ε = 0.75）的阿秒脉冲的潜力。这种创建手性敏感元件的新方法提供了一个简单实用的旋钮，以平滑且可预测的方式控制组合谐波场的偏振。
