Song Xiaohong, Zuo Ruixin, Yang Shidong, Li Pengcheng, Meier Torsten, Yang Weifeng
Opt Express. 2019 Feb 4;27(3):2225-2234. doi: 10.1364/OE.27.002225.
High order harmonic generation (HHG) in semiconductors opens a new frontier in strong field physics and attosecond science. However, the underlying physical mechanisms are not yet fully understood and lively debated. Here, we identify and discuss carrier-wave population transfer as a novel and important dynamical effect. We find that the interband excitation occurs in an extremely short time window due to the intraband motion. Our analysis based on this finding allows for a physically intuitive interpretation of the anomalous carrier-envelope phase dependence observed in HHG from MgO and to understand the dominant role of the interband polarization as reported in a series of recent semiconductor HHG experiments. Motivated by the discovered coupling mechanism, we demonstrate that the interband excitation can be controlled by an appropriately tailored two-color field. An ultrabroad supercontinuum spectrum covering the entire plateau region can be generated which directly creates an isolated-attosecond pulse even without phase compensation. Our results provide remarkable insight into the basic physics governing the sub-cycle electron motion with significant implications for the generation of isolated-attosecond light pulses in semiconductor materials.
半导体中的高次谐波产生（HHG）为强场物理和阿秒科学开辟了一个新的前沿领域。然而，其潜在的物理机制尚未得到充分理解，仍存在激烈的争论。在此，我们识别并讨论载波布居转移这一新颖且重要的动力学效应。我们发现，由于带内运动，带间激发在极短的时间窗口内发生。基于这一发现的分析能够对在MgO的HHG中观察到的反常载波包络相位依赖性进行物理直观的解释，并理解一系列近期半导体HHG实验中所报道的带间极化的主导作用。受所发现的耦合机制的启发，我们证明带间激发可以通过适当定制的双色场来控制。可以产生覆盖整个平台区域的超宽超连续谱，即使在没有相位补偿的情况下也能直接产生孤立阿秒脉冲。我们的结果为支配亚周期电子运动的基本物理提供了显著的见解，对半导体材料中孤立阿秒光脉冲的产生具有重要意义。
