通过螺旋度分辨高次谐波产生实现谷极化的全光重构

中文摘要 AI 辅助

我们从理论上研究了带隙石墨烯在椭圆偏振激光场驱动下的谷分辨高次谐波产生。采用两带密度矩阵模拟与电子-空穴复合轨迹模型，发现两个不等价谷会发射具有相反螺旋度的谐波；在椭圆偏振场下，这些发射主要发生在激光场的不同半周期内。针对单层MoS₂的含时密度泛函理论计算显示，谐波发射存在相同的时间分离与相反螺旋度，支持这种谷依赖手性响应的普适性。我们进一步提出一种全光方案，用于从螺旋度分辨的谐波信号中重构谷极化：首先用圆偏振脉冲制备谷布居失衡，随后的椭圆偏振激光通过泡利阻塞对相反螺旋度的谐波强度产生不同变化，这些强度变化的比值可直接衡量谷极化。我们的结果表明，手性高次谐波发射可作为超快谷依赖载流子动力学的全光探针。

英文摘要

We theoretically investigate valley-resolved high-order harmonic generation in gapped graphene driven by elliptically polarized laser fields. Using two-band density-matrix simulations and an electron-hole recombination trajectory model, we find that the two inequivalent valleys emit harmonics with opposite helicities. Under an elliptically polarized field, these emissions occur predominantly in different half cycles of the laser field. Time-dependent density functional theory calculations for monolayer MoS$_2$ show the same temporal separation of harmonic emissions with opposite helicities, supporting the generality of this valley-dependent chiral response. We further propose an all-optical scheme to reconstruct valley polarization from helicity-resolved harmonic signals. A circularly polarized pulse first prepares a valley population imbalance. A subsequent elliptically polarized laser induces different changes in the harmonic intensities of opposite helicities through Pauli blocking. The ratio of these intensity changes provides a direct measure of the valley polarization. Our results demonstrate that chiral high-harmonic emission can serve as an all-optical probe of ultrafast valley-dependent carrier dynamics.

发表机构

• College of Physics Science and Technology, Hebei University（河北大学物理科学与技术学院）

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