The use of few-femtosecond, extreme ultraviolet (XUV) pulses, produced by high-order harmonic generation, in combination with few-femtosecond infrared (IR) pulses in pump–probe experiments has great potential to disclose ultrafast dynamics in molecules, nanostructures and solids. A crucial prerequisite is a reliable characterization of the temporal properties of the XUV and IR pulses. Several techniques have been developed. The majority of them applies phase reconstruction algorithms to a photoelectron spectrogram obtained by ionizing an atomic target in a pump–probe fashion. If the ionizing radiation is a single harmonic, all the information is encoded in a two-color two-photon signal called sideband (SB). In this work, we present a simplified model to interpret the time-frequency mapping of the SB signal and we show that the temporal dispersion of the pulses directly maps onto the shape of its spectrogram. Finally, we derive an analytical solution, which allows us to propose a novel procedure to estimate the second-order dispersion of the XUV and IR pulses in real time and with no need for iterative algorithms.

在泵-探针实验中使用由高次谐波产生的几飞秒极紫外 (XUV) 脉冲与几飞秒红外 (IR) 脉冲相结合，具有揭示分子、纳米结构和超快动力学的巨大潜力。固体。一个关键的先决条件是 XUV 和 IR 脉冲的时间特性的可靠表征。已经开发了几种技术。他们中的大多数将相位重建算法应用于通过以泵-探针方式电离原子目标而获得的光电子谱图。如果电离辐射是单次谐波，则所有信息都编码在称为边带 (SB) 的双色双光子信号中。在这项工作中，我们提出了一个简化模型来解释 SB 信号的时频映射，我们表明脉冲的时间色散直接映射到其频谱图的形状上。最后，我们推导出了一个解析解，这使我们能够提出一种新的程序来实时估计 XUV 和 IR 脉冲的二阶色散，而无需迭代算法。