发表机构
RIKEN Center for Advanced Photonics, RIKEN; Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences; University of Chinese Academy of Sciences（理化学研究所先进光子学中心; 中国科学院西安光学精密机械研究所; 中国科学院大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究开发基于强场近似的复门全光频率分辨光学开关技术，实验表征中红外亚周期激光产生的100-180 eV超宽带孤立阿秒脉冲，测得其持续时间约300 as，证实该技术可用于相关阿秒源的时间表征。
AI 中文摘要
我们实验演示了全光频率分辨光学开关（AO-FROG）技术，用于表征由中红外亚周期激光场产生的超宽带孤立阿秒脉冲（IAPs）。通过将AO-FROG框架扩展至超出传统仅相位调制近似的范围，我们开发了基于强场近似（SFA）的理论框架，并证明在高次谐波产生过程中，弱扰动场会同时诱导相位和振幅调制。因此，需要复值门函数以实现精确的脉冲重建。利用2.26μm亚周期驱动激光，我们在氩气中表征了能量范围为100-180 eV的IAPs。测得的AO-FROG迹线显示出延迟相关的光谱调制，这源于扰动引起的电子轨迹和电离概率的改变。SFA模拟再现了实验观测结果，并证实了纳入电离诱导振幅调制的重要性。重建的时间和光谱特性揭示了IAP的持续时间约为300 as及其光谱相位，从而可获取所产生脉冲的阿秒啁啾信息。我们的研究结果确立了AO-FROG作为一种有前景的方法，可用于表征长波长红外场驱动的超宽带阿秒源的时间特性。
英文摘要
We experimentally demonstrate all-optical frequency-resolved optical gating (AO-FROG) for the characterization of ultrabroadband isolated attosecond pulses (IAPs) generated by a mid-infrared sub-cycle laser field. By extending the AO-FROG framework beyond the conventional phase-only modulation approximation, we develop a strong-field approximation (SFA)-based theoretical framework and show that the weak perturbing field induces both phase and amplitude modulations during high-order harmonic generation. A complex-valued gate function is therefore required for accurate pulse reconstruction. Using a 2.26-$μ$m sub-cycle driving laser, we characterize IAPs spanning 100-180 eV in argon. The measured AO-FROG traces exhibit delay-dependent spectral modulations arising from perturbation-induced modifications of the electron trajectories and ionization probability. SFA simulations reproduce the experimental observations and confirm the importance of including ionization-induced amplitude modulation. The reconstructed temporal and spectral properties reveal an IAP duration of approximately 300 as and its spectral phase, providing access to the attosecond chirp of the generated pulses. Our results establish AO-FROG as a promising approach for temporal characterization of ultrabroadband attosecond sources driven by long-wavelength infrared fields.
Comments11 pages, 4 figures
