双色场下MoS_(2)高次谐波产生的调制特性  

Modulation Characteristics of High-Order Harmonic Generation in MoS_(2) Under Bichromatic Fields

作　　者：楼国聪 刘灿东[1,2] 郑颖辉 Lou Guocong;Liu Candong;Zheng Yinghui(State Key Laboratory of High Field Laser Physics,Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences,Shanghai 201800,China;Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China;Zhangjiang Laboratory,Shanghai 201210,China)

机构地区：[1]中国科学院上海光学精密机械研究所强场激光物理国家重点实验室,上海201800 [2]中国科学院大学材料科学与光电工程中心,北京100049 [3]张江实验室,上海201210

出　　处：《光学学报》2024年第16期1-10,共10页Acta Optica Sinica

基　　金：国家自然科学基金(12174413);受张江实验室支持。

摘　　要：使用紧束缚近似和速度规范下的密度矩阵方程对双色强激光场下单层MoS_(2)产生的高次谐波进行理论计算,通过调整双色场的延迟来观测高次谐波产生的强度随延迟的变化,发现在不同的驱动场偏振方向下高次谐波的振荡周期不同,并提出一个直观的模型来解释这一现象。当驱动场偏振沿Γ—M方向时,高次谐波的振荡周期会受到倍频光和基频光强度比的影响,从一个基频光周期内振荡2次变成振荡4次,这与倍频光和基频光的竞争有关。此外,研究了分别平行和垂直于驱动场偏振方向的偶次谐波振荡的振幅和相位信息,发现这两个方向的偶次谐波振荡相位受倍频光和基频光强度比的影响不同,这与它们的产生机制有关。理论计算表明,使用双色场作为驱动场不仅有助于理解材料反演对称性的结构信息,还有助于进一步理解固体材料中的电子动力学过程。Objective In recent years,with the development of mid-infrared laser technology,experimental measurements of solid-state high-order harmonics have been conducted in various materials,such as crystalline materials,two-dimensional materials,and topological materials.Compared to gases,solid-state high-order harmonics exhibit unique properties,including even-order harmonic generation,linear cutoff law,anomalous ellipticity dependence,and multi-plateau structures.Among these materials,monolayer MoS_(2) as a direct bandgap two-dimensional material possesses large exciton binding energy and strong spin-orbit coupling effects.Due to the breaking of inversion symmetry,its Brillouin zone contains two inequivalent energy valleys of K and K'.The rich characteristics of monolayer MoS_(2) have brought extensive research in recent years.Therefore,we employ tight-binding approximation and the density matrix equation under the velocity gauge to theoretically calculate the high-order harmonics generated in monolayer MoS_(2) under a bichromatic field.By adjusting the bichromatic field delay,we observe the intensity of the generated high-order harmonics as a function of the delay.We find that under different driving field polarization directions,the oscillation period of the high-order harmonics varies.Additionally,we propose an intuitive model to explain this phenomenon.Furthermore,we extract the amplitude and phase information of even-order harmonic oscillations parallel and perpendicular to the polarization direction of the driving field.We discover that the intensity ratio of the second harmonic with respect to the fundamental field exerts different effects on the phase of the even-order harmonic in parallel and perpendicular directions.Our theoretical calculations indicate that adopting a bichromatic field as the driving field for interacting with monolayer MoS_(2) not only introduces the competition between the incident field and the medium’s inversion symmetry but also encompasses the contribution of Berry curvature in the

关 键 词：原子与分子物理学 双色场 固体高次谐波 振荡周期 振荡相位 

分 类 号：O437[机械工程—光学工程]