激光致声混凝土内部空洞检测技术是一种针对混凝土脱空鼓包现象的遥感检测技术，具有检测快速，非接触等特点，满足了在一些不方便进行接触式检测的场景下对混凝土内部空洞进行识别的需求。该技术的实现主要分为声波的激发以及声波的探测。文中聚焦声波激发这一部分，用加速度传感器替代激光测振仪，搭建了一套激光致声混凝土内部空洞检测系统，并对内部预制空洞的混凝土试块进行了检测。实验发现混凝土内部空洞的存在会改变空洞上方结构的抗弯刚度，当存在外部激励时，空洞上方的结构将会出现弯曲振动的现象，该振动的频率接近于振动结构的一阶固有频率。使用高功率密度的脉冲激光器可以方便地激发出缺陷区域的弯曲振动，当空洞缺陷较浅时，可以根据弯曲振动在频域的特征响应判断内部是否存在空洞。随着空洞深度的增加，空洞上方结构的抗弯刚度逐渐增强，弯曲振动的振幅减小，仅凭特征频率将难以实现内部空洞的识别。在这种情况下，可以利用表面振动信号的加速度能量谱来表征振动能量，通过振动能量的高低判断混凝土内部是否存在空洞。基于上述理论，成功探测到了混凝土内部深度为150 mm的空洞，验证了利用激光致声技术检测混凝土内部空洞的可行性。

报道了一款基于调制共振泵浦技术的Nd:YVO₄自拉曼激光器。针对全固态自拉曼激光器中热效应严重导致的激光器输出功率及光光效率普遍偏低的问题，合理地将共振泵浦技术和调制泵浦技术相结合，实现了激光器的有效热管控，缓解了激光器的热效应，提高了泵浦上限，从而实现了激光器输出功率和光光效率的大幅提高。当泵浦源的调制频率为10 kHz、占空比为40%、平均泵浦功率为30 W、声光Q开关的调制频率为100 kHz时，获得了最大平均功率为8.57 W的1176 nm斯托克斯光输出，相应光光转换效率28.6%。相较于相同泵浦功率的连续泵浦机制下的实验结果，斯托克斯光平均输出功率提高了42%，光光效率提高了8.5%。实验结果表明：共振泵浦和调制泵浦技术相结合的方式可以有效缓解热效应，提高泵浦功率上限，从而提高自拉曼激光器的输出功率和光光效率。

The spiderlike structures in the photoelectron momentum distributions of ionized electrons from the hydrogen atom are numerically simulated by using a semiclassical rescattering model (SRM) and solving the time-dependent Schr?dinger equation (TDSE), focusing on the role of the phase of the scattering amplitude. With the SRM, we find that the spiderlike legs shift to positions with smaller transverse momentum values while increasing the phase. The spiderlike patterns obtained by SRM and TDSE are in good agreement upon considering this phase. In addition, the time differences in electron ionization and rescattering calculated by SRM and the saddle-point equations are either in agreement or show very similar laws of variation, which further corroborates the significance of the phase of the scattering amplitude.

The carrier envelope phase (CEP) has a direct impact on the physical properties of an isolated attosecond pulse (IAP) and many strong field processes, but it is difficult to measure in reality. Aiming at obtaining more accurate and complete characterization of CEP, we numerically investigate the annular photoelectron momentum spectra of the hydrogen atom ionized by overlapped fields of an IAP and an infrared (IR) pulse. By defining an overlapping parameter, the momentum patterns are classified and optimized for unambiguously measuring the rotation angle of a momentum pattern versus the CEP value. A series of simulations verify its robustness.

The photoionization by two elliptically polarized, time delayed attosecond pulses is investigated to display a momentum distribution having the helical vortex or ring structures. The results are obtained by the strong field approximation method and analyzed by the pulse decomposition. The ellipticities and time delay of the two attosecond pulses are found to determine the rotational symmetry and the number of vortex arms. For observing these vortex patterns, the energy bandwidth and temporal duration of the attosecond pulses are ideal.