以晶面<100>的硅片为研究对象，使用重复频率1 kHz的超快复合双脉冲作为激发工具，通过研究双脉冲之间的偏振夹角、延迟时间和脉冲数对周期性结构面积的影响，探究引起周期性结构演化的非线性电离动力学。实验结果表明，在激光能量密度为0.23 J/cm²、脉冲组合为100个的复合脉冲辐照条件下，正交偏振诱导的结构面积最小，相比于其他入射形式下诱导的最大面积减小率约为45%，这是因为局域场的反复调制抑制了周期性结构边缘烧蚀阈值的降低。在正交偏振时，随着两束脉冲之间延迟时间的改变，通过观察诱导结构面积变化可以分析从电子电离到物质喷发的连续过程。该复合脉冲调控技术可为研究超快激光诱导半导体表面周期性结构的偏振依赖性与电子电离效率提供参考，进一步的改进有望实现超衍射极限结构的快速诱导。

We designed a femtosecond (fs) + picosecond (ps) double-pulse sequence by using a Mach–Zehnder-like apparatus to split a single 120 fs pulse into two sub-pulses, and one of them was stretched to a width of 2 ps by a four-pass grating system. Through observing the ripples induced on the ZnO surface, we found the ionization rate appeared to be higher for the sequence in which the fs pulse arrived first. The electron rate equation was used to calculate changes of electron density distribution for the sequences with different delay times. We suggest that using a temporally shaped fs+ps pulse sequence can achieve nonlinear ionization control and influence the induced ripples.

Based on Kogelnik’s coupled-wave theory, it is found that when a femtosecond pulse is incident on a transmitted volume holographic grating, two transverse standing waves along the grating vector direction will be generated inside the volume holographic grating (VHG). Due to field localization of two standing waves, they have two different velocities along the propagation depth. On the output plane of the VHG, femtosecond dual pulses are generated in both the diffracted and transmitted directions. Results show that the pulse interval is determined by the refractive index modulation and thickness of the grating, while the waveform of the dual pulses is independent of the grating parameters.

Spatio-temporal coupling characteristics of ultrafast laser pulses are quantitatively tailored. An asymmetric microstructure is induced in the focal volume when the laser scans perpendicularly to the direction of the spatial chirp in fused silica. The tilted direction reverses when adding a Dove prism into the light path. The sign of the pulse front tilt can be turned from positive to negative by changing the group delay dispersion by steps. We reveal that the tilted direction of a microstructure depends on spatial chirp, and the interplay between spatio-temporal chirp leads to the change of tilted angles.