近日，意大利米兰理工大学的Mauro Nisoli及其研究小组与西班牙萨拉曼卡大学的Carlos Hernández-García等人合作并取得一项新进展。经过不懈努力，他们通过时间门控相位匹配驱动半无限气室中孤立阿秒脉冲的产生。相关研究成果已于2024年8月20日在国际知名学术期刊《光：科学与应用》上发表。

该研究团队提供了在半无限气室中产生孤立极紫外阿秒脉冲的明确实验证据，证明了扩展介质几何结构可有效用于产生孤立阿秒脉冲（IAPs）。为了更深入地理解这一现象，研究人员开发了一种高阶谐波产生（HHG）的模拟方法，该方法将非线性传播与宏观HHG相结合，在单原子层面求解三维含时薛定谔方程。

这项模拟结果表明，实验中观察到的作为明亮等离子体通道存在的驱动场的非线性时空重塑，作为一种自我调节机制，有助于改善IAPs产生的相位匹配条件。

据悉，孤立阿秒脉冲（IAP）的产生通常需要使用在高压下运行的中短气室。相比之下，人们普遍认为，由于非线性现象对良好相位匹配条件的挑战，低压下的中长方案本质上不适合用于IAP的产生。

附：英文原文

Title: Isolated attosecond pulse generation in a semi-infinite gas cell driven by time-gated phase matching

Author: Vismarra, Federico, Fernndez-Galn, Marina, Mocci, Daniele, Colaizzi, Lorenzo, Segundo, Vctor Wilfried, Boyero-Garca, Roberto, Serrano, Javier, Conejero-Jarque, Enrique, Pini, Marta, Mai, Lorenzo, Wu, Yingxuan, Wrner, Hans Jakob, Appi, Elisa, Arnold, Cord L., Reduzzi, Maurizio, Lucchini, Matteo, San Romn, Julio, Nisoli, Mauro, Hernndez-Garca, Carlos, Borrego-Varillas, Roco

Issue&Volume: 2024-08-20

Abstract: Isolated attosecond pulse (IAP) generation usually involves the use of short-medium gas cells operated at high pressures. In contrast, long-medium schemes at low pressures are commonly perceived as inherently unsuitable for IAP generation due to the nonlinear phenomena that challenge favourable phase-matching conditions. Here we provide clear experimental evidence on the generation of isolated extreme-ultraviolet attosecond pulses in a semi-infinite gas cell, demonstrating the use of extended-medium geometries for effective production of IAPs. To gain a deeper understanding we develop a simulation method for high-order harmonic generation (HHG), which combines nonlinear propagation with macroscopic HHG solving the 3D time-dependent Schrdinger equation at the single-atom level. Our simulations reveal that the nonlinear spatio-temporal reshaping of the driving field, observed in the experiment as a bright plasma channel, acts as a self-regulating mechanism boosting the phase-matching conditions for the generation of IAPs.

DOI: 10.1038/s41377-024-01564-5

Source: https://www.nature.com/articles/s41377-024-01564-5