量子轨道调控固体高次谐波辐射的理论研究

High-order harmonics generation (HHG) is the principal route to produce the attosecond coherent source which has significant applications in the ultrafast optical physics, material science and technology and biological imaging. Recently, HHG in solids driven by the ultrafast laser fields possesses a series of unique characteristics which are different from those in gas. In addition, these findings are expected to conquer the lower efficiency of the harmonic conversion in the gas phase, but directly challenge the application of the physical picture responsible for the HHG from gas in solids. Based on the theory of the solid-state physics, we will study the ultrafast dynamics of the quasiparticle in solids and further control the emissions of high-order harmonics. Firstly, the scattering processes among quasiparticles, laws for the recombination of electron-hole pair and the nonequilibrium transport of carrier in the momentum space will be investigated to detect their corresponding signatures in the spectroscopy of HHG from solids. Secondly, quantum-path interference between wave packets ionized from the different peaks of the laser pulses will be studied. Finally, by adopting the Wannier state in the real space, we will explore the physical picture for the ultrafast dynamics of quasiparticle and provide the better insights on the mechanisms of the high-order harmonic generation in solids. All the above studies would allow us to accurately modulate the emissions of high-order harmonics in spatiotemporal domains, obtain the coherent source with shorter wavelength and higher efficiency and further establish new spectroscopic method to probe the interactions between quasiparticles in the solid materials.

高次谐波是当前产生阿秒相干光源的主要途径，阿秒相干光源在超快光物理、材料科学技术和生物成像等领域有重要的应用价值。近年来，超快激光驱动固体产生的高次谐波具有一系列不同于气体高次谐波的特性。这些特性的发现有望被用于突破气体高次谐波产率低的瓶颈，但对气体高次谐波产生的物理图像在固体谐波中的适用提出了挑战。本项目将基于固体理论研究固态物质内的准粒子超快动力学以便实现对固体谐波辐射的量子相干调控。首先在动量空间研究准粒子间的散射、电子-空穴的复合和载流子非平衡输运在高次谐波光谱中呈现的特性和规律。在此基础上，研究激光脉冲的不同峰值时刻电离电子波包间的量子轨道干涉。最后在实空间采用万尼尔态研究准粒子超快动力学的物理图像，并进一步揭示固体高次谐波的产生机制。本项目将实现涵盖时空的四维空间调控谐波辐射，产生高效的、短波长相干光源。此外，本项目还将构建全新的光学方法探测固态物质内准粒子间的相互作用。

高次谐波是目前产生阿秒光源的主要途径，其中的光谱还携带了凝聚态系统的超快准粒子动力学信息。本项目以量子轨道相干调控为目标，细致地研究了固体高次谐波的辐射过程。我们通过聚焦量子轨道的退相干效应，建立了开放轨道模型，并且对于晶格振动诱导的量子退相干效应作了新解读。在所有团队成员的共同努力下，我们圆满地完成了原定的研究目标。此外，我们还将研究内容拓展到了量子拓扑系统，发现量子体系的对称性破缺效应能有效地增强高次谐波的辐射效率，为拓扑边界电子动力学的相干控制铺平了道路。在项目的资助下我们发表Physical Review A/B 5篇，Optics Letters 1篇，共计SCI论文7篇，并受邀在重要学术会议上作口头报告，培养硕士研究生1名。该项目的研究结果可用于新兴光电器件、极紫外光源等方面的应用。