超强超短激光在空间上具有大口径、在时间上具有短脉冲，因此极易产生时空耦合效应，例如脉冲前沿畸变，使得脉冲前沿和相位前沿发生时空分离，通常表现为脉冲前沿倾斜或弯曲，不利于获得预期的高聚焦光强。但当这种脉冲前沿畸变（控制）用于产生X形光波包时，却增加了一维全新的自由度，实现了光波包群速度和群加速度的自由控制，可获得超光速、亚光速、加速、减速，甚至动态可控的群速度。通过综述脉冲前沿畸变（控制）在超强超短激光中的不良影响和在X形光波包中的特殊效果，旨在为同一光学现象在不同研究方向间的交叉应用提供些许思考。

逆康普顿散射源是利用高能电子束和强激光对撞产生高能辐射的光源。传统电子加速器作为电子源的逆康普顿散射源体积庞大，难以推广。而新型的激光等离子体电子加速器具有更高的加速梯度，具备小型化的发展潜力。全光逆康普顿散射源就是一种基于激光等离子体电子加速器实现的小型化高能辐射源，具有更短脉宽、更高亮度的辐射输出，应用前景十分广阔。首先，总结了全光逆康普顿散射源在提高亮度、能量和单能性等方面的优化研究进展，并分析了设计重点；最后，介绍了全光逆康普顿散射源在基础科学研究、工业和生物医学领域的典型应用。

利用百太瓦级激光系统在氖气（Ne）中得到基于高次谐波产生的极紫外脉冲。通过松聚焦结构在13 nm波段产生单级次单脉冲能量为13.5 nJ（13.1 nm波长）和11.1 nJ（13.5 nm波长）的高次谐波辐射，转换效率为3.6×10-7和3.0×10-7，谐波发散角的半高全宽为0.32 mrad和0.33 mrad。对含时薛定谔方程进行数值求解，得到单原子偶极发射谱，结合麦克斯韦方程组模拟传播效应，同时考虑气体对谐波的吸收效应，理论模拟得到的信号强度随气压和光强的变化趋势与实验结果基本符合。实现相位匹配的谐波光束质量很好，纵向空间分布为高斯型。结合相位匹配条件和空间分布的分析得到了目前激光参数下的最优相位匹配条件。这种基于高次谐波机制的高能量相干极紫外光源在作为自由电子激光的种子光源以及超快非线性实验和半导体工业检测等方面具有广阔的应用前景。

Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequency-dependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light field is usually determined by the complex refractive index $\tilde{n}$. The absorption signal is directly related to the imaginary part of $\tilde{n}$, namely, the absorption index. The real part of $\tilde{n}$ refers to the real refractive index, which describes the chromatic dispersion of an optical material. However, the real refractive index information is usually not available in conventional absorption experiments. Here, we investigate the refractive index line shape in ultrafast XUV transient absorption spectroscopy by using a scheme that the XUV pulse traverses the target gas jet off-center. The jet has a density gradient in the direction perpendicular to the gas injection direction, which induces deflection on the XUV radiation. Our experimental and theoretical results show that the shape of the frequency-dependent XUV deflection spectra reproduces the refractive index line profile. A typical dispersive refractive index line shape is measured for a single-peak absorption; an additional shoulder structure appears for a doublet absorption. Moreover, the refractive index line shape is controlled by introducing a later-arrived near-infrared pulse to modify the phase of the XUV free induction decay, resulting in different XUV deflection spectra. The results promote our understanding of matter-induced absorption and deflection in ultrafast XUV spectroscopy.