OP: Mechanisms and Phase Matching of Below-Threshold High-Order Harmonic Generation in Solids

OP：固体中阈值以下高次谐波产生的机制和相位匹配

• 批准号: 1806135
• 负责人: Michael Chini
• 金额: $ 25万
• 依托单位: The University of Central Florida Board of Trustees
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-01 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1806135&HistoricalAwards=false
• 关键词: OP; Mechanisms; Phase; Matching; Below

The purpose of this project is to study the fundamental response of electrons in solid crystals to intense laser pulses, which results in the emission of high-frequency "harmonic" light flashes lasting only a few hundreds of attoseconds (1 attosecond is a "nano-nanosecond", or 0.000000000000000001 seconds). The mechanisms of the light emission have been studied in gaseous materials over the previous two decades and are now fairly well understood. This understanding has enabled widespread adoption of gas-phase harmonics to time-resolved studies of electron motion and high-resolution imaging applications. In solids, however, the mechanisms of harmonic emission can be hidden from experiments, since both the low-frequency laser and the high-frequency harmonics have to travel through the crystal. In this project, the group will use innovative laser techniques to extract the ultrafast electron motion in solid crystals from measurements of the emitted light and use the knowledge we obtain to develop more efficient harmonic light sources based on thin film materials. The results of the research will advance scientific knowledge of intense laser interactions with materials and will be important to future development of high-speed electronic devices based on laser-driven currents. Students involved in the project will learn advanced optical, electronics, and computational techniques, gaining the experience necessary to develop and advance these next-generation technologies from high-tech industries. High-order harmonic emission from solid crystals was first observed in 2011 by irradiating bulk zinc oxide (ZnO) crystals with mid-infrared femtosecond laser pulses. Since then, several models describing the electron dynamics underlying solid-state high-order harmonic generation have been proposed. One highly successful model which has been used to interpret experiments in ZnO and other wide-band gap semiconductors involves a semiclassical "generalized recollision" process similar to gas-phase high-order harmonic generation: charge carriers are first excited via tunneling in the strong laser field. The electrons and holes are then accelerated in their respective bands by the laser field, until they re-encounter one another, recombine, and emit a high-frequency photon. The group will: investigate the physics of high-order harmonic generation in wide bandgap semiconductors driven by mid-infrared laser pulses, with the goals of classifying the mechanisms through which high-order harmonics are generated and phase matched in solids; identify signatures of the generalized recollision and other proposed mechanisms which will be tested through spatially- and spectrally-resolved measurements of the high-order harmonics generated in a variety of crystals using a two-color laser field; focus attention to both the above- and below-threshold harmonics, with respective photon energies larger and smaller than the material's band gap, since the recollision picture which has been used to describe above-threshold harmonic generation is expected to break down for below-threshold harmonics; and investigate the role of propagation of the intense laser pulses and generated harmonics in the crystal, through experimental studies and simulations, with the goal of enhancing the harmonic emission through phase matching.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目的目的是研究固体晶体中电子对强激光脉冲的基本响应，这种响应导致发射高频“谐波”闪光，持续时间只有几百阿秒（1阿秒是“纳米纳秒”，即0.000000000000000001秒）。在过去的二十年里，人们已经研究了气态物质的光发射机制，现在已经很好地理解了。这种理解使得气相谐波广泛应用于电子运动的时间分辨研究和高分辨率成像应用。然而，在固体中，谐波发射的机制可以从实验中隐藏，因为低频激光和高频谐波都必须穿过晶体。在这个项目中，该小组将使用创新的激光技术从发射光的测量中提取固体晶体中的超快电子运动，并利用我们获得的知识开发基于薄膜材料的更有效的谐波光源。该研究结果将推进激光与材料强烈相互作用的科学知识，并将对基于激光驱动电流的高速电子器件的未来发展具有重要意义。参与该项目的学生将学习先进的光学、电子和计算技术，获得开发和推进高科技行业下一代技术所需的经验。2011年，用中红外飞秒激光脉冲照射大块氧化锌（ZnO）晶体，首次观测到固体晶体的高次谐波发射。从那时起，已经提出了几个描述固态高次谐波产生的电子动力学的模型。一个非常成功的模型已经用于解释ZnO和其他宽带隙半导体的实验，涉及类似于气相高次谐波产生的半经典“广义回忆”过程：电荷载流子首先通过强激光场的隧道激发。然后，电子和空穴在各自的波段被激光场加速，直到它们再次相遇，重新组合，并发射出高频光子。该小组将：研究中红外激光脉冲驱动的宽带隙半导体中高次谐波产生的物理学，目标是分类高次谐波在固体中产生和相位匹配的机制；通过使用双色激光场对各种晶体中产生的高次谐波进行空间和光谱分辨测量，确定广义回忆和其他提出机制的特征；将注意力集中在阈值以上和阈值以下的谐波上，各自的光子能量大于或小于材料的带隙，因为用于描述阈值以上谐波产生的回忆图预计会被阈值以下的谐波分解；并通过实验研究和仿真，探讨强激光脉冲在晶体中的传播及其产生的谐波在晶体中的作用，以期通过相位匹配来增强谐波发射。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Crystal symmetry and polarization of high-order harmonics in ZnO

• DOI: 10.1088/1361-6455/ab470d
• 发表时间: 2019-11-28
• 期刊: JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
• 影响因子: 1.6
• 作者: Jiang, Shicheng;Gholam-Mirzaei, Shima;Lin, C. D.
• 通讯作者: Lin, C. D.

High Harmonic Generation from Thin Film ZnO in Transmission Geometry

传输几何中薄膜 ZnO 的高次谐波产生

• DOI: 10.1364/cleo_at.2023.jw2a.58
• 发表时间: 2023
• 期刊: Optica Publishing Group
• 作者: Journigan, Troie;Liu, Yangyang;Cabello, Christian;Berriel, S Novia;Banerjee, Parag;Chini, Michael
• 通讯作者: Chini, Michael

High Harmonic Generation from Thin Film LiNbO3

薄膜 LiNbO3 产生高次谐波

• DOI: 10.1364/ls.2020.lw1g.4
• 发表时间: 2020
• 期刊: Frontiers in Optics/Laser Science
• 作者: Journigan, Troie;Gholam-Mirzaei, Shima;Crites, Erin;Turkowski, Volodymyr;Sjaardema, Tracy;Fathpour, Sasan;Chini, Michael
• 通讯作者: Chini, Michael

Symmetry and Polarization of High-Order Harmonic Generation from Solids

固体高次谐波产生的对称性和偏振

• DOI: 10.1364/cleo_qels.2019.fm4m.4
• 发表时间: 2019
• 期刊: CLEO: QELS_Fundamental Science 2019
• 作者: Gholam-Mirzaei, Shima;Jiang, Shicheng;Crites, Erin;Beetar, John E.;Lu, Ruifeng;Lin, C. D.;Chini, Michael
• 通讯作者: Chini, Michael

Carrier Envelope Phase Dependence of High-Order Harmonic Generation from ZnO

ZnO 产生高次谐波的载波包络相位依赖性

• DOI: 10.1364/cleo_fs.2023.fw3m.5
• 发表时间: 2023
• 期刊: Optica Publishing Group
• 作者: Journigan, Troie;Liu, Yangyang;Cabello, Christian;Truong, Tran Chau;Khatri, Dipendra;Berriel, S Novia;Banerjee, Parag;Chini, Michael
• 通讯作者: Chini, Michael