Random lasers are a type of lasers that lack typical resonator structures, offering benefits such as easy integration, low cost, and low spatial coherence. These features make them popular for speckle-free imaging and random number generation. However, due to their high threshold and phase instability, the production of picosecond random lasers has still been a challenge. In this work, we have developed three dyes incorporating polymer optical fibers doped with various scattering nanoparticles to produce short-pulsed random fiber lasers. Notably, stable picosecond random laser emission lasting 600 ps is observed at a low pump energy of 50 µJ, indicating the gain-switching mechanism. Population inversion and gain undergo an abrupt surge as the intensity of the continuously pumped light nears the threshold level. When the intensity of the continuously pumped light reaches a specific value, the number of inversion populations in the “scattering cavity” surpasses the threshold rapidly. Simulation results based on a model that considers power-dependent gain saturation confirmed the above phenomenon. This research helps expand the understanding of the dynamics behind random medium-stimulated emission in random lasers and opens up possibilities for mode locking in these systems.

We present a high-energy, hundred-picosecond (ps) pulsed mid-ultraviolet solid-state laser at 266 nm by a direct second harmonic generation (SHG) in a barium borate (BaB₂O₄, BBO) nonlinear crystal. The green pump source is a 710 mJ, 330 ps pulsed laser at a wavelength of 532 nm with a repetition rate of 1 Hz. Under a green pump energy of 710 mJ, a maximum output energy of 253.3 mJ at 266 nm is achieved with 250 ps pulse duration resulting in a peak power of more than 1 GW, corresponding to an SHG conversion efficiency of 35.7% from 532 to 266 nm. The experimental data were well consistent with the theoretical prediction. To the best of our knowledge, this laser exhibits both the highest output energy and highest peak power ever achieved in a hundred-ps/ps regime at 266 nm for BBO-SHG.

Achieving an all-fiber ultra-fast system with above kW average power and mJ pulse energy is extremely challenging. This paper demonstrated a picosecond monolithic master oscillator power amplifier system at a 25 MHz repetition frequency with an average power of approximately 1.2 kW, a pulse energy of approximately 48 μJ and a peak power of approximately 0.45 MW. The nonlinear effects were suppressed by adopting a dispersion stretched seed pulse (with a narrow linewidth of 0.052 nm) and a multi-mode master amplifier with an extra-large mode area; then an ultimate narrow bandwidth of 1.32 nm and a moderately broadened pulse of approximately 107 ps were achieved. Meanwhile, the great spatio-temporal stability was verified experimentally, and no sign of transverse mode instability appeared even at the maximum output power. The system has shown great power and energy capability with a sacrificed beam propagation product of 5.28 mm $\cdot$ mrad. In addition, further scaling of the peak power and pulse energy can be achieved by employing a lower repetition and a conventional compressor.

Parametric interaction allows both forward and backward energy transfers among the three interacting waves. The back-conversion effect is usually detrimental when unidirectional energy transfer is desired. In this theoretical work, we manifest that the back-conversion effect underpins the direct generation of the picosecond pulse train without the need for a laser resonator. The research scenario is an optical parametric amplification (OPA) that consists of a second-order nonlinear medium, a quasi-continuous pump laser and a sinusoidal amplitude-modulated seed signal. The back-conversion of OPA can transfer the modulation peaks (valleys) of the incident signal into output valleys (peaks), which inherently induces spectral sidebands. The generation of each sideband is naturally accompanied with a phase shift of ±π. In the regime of full-back-conversion, the amount and amplitude of the sidebands reach the maximum simultaneously, and their phase constitutes an arithmetic sequence, leading to the production of a picosecond pulse train. The generated picosecond pulse train can have an ultrahigh repetition rate of 40 GHz or higher, which may facilitate ultrafast applications with ultrahigh speed.

为了实现高速度切割碳化硅（SiC）晶圆，采用自行研制的高能量皮秒脉冲光纤激光器进行了隐形切割实验。依据切片的截面形貌、表面热损伤区和边缘直线度，分析了皮秒激光器的切割结果，并探究了单脉冲能量和扫描速度对切片质量的影响。结果表明，当使用中心波长为1030 nm、重复频率为100 kHz、单脉冲能量为20 μJ、脉冲宽度约为100 ps的皮秒脉冲隐形切割360 μm厚度的SiC晶圆时，切片的质量能够满足实际应用要求，且激光的扫描速度可达400 mm/s，相应的切割速度为44.44 mm/s，高于其他相关报道。

红外器件的封装中常需用一些透明材料制成零部件，适合采用脉冲激光对其进行切割和标刻加工，但需要对加工参数进行精细优化。文中以在用于红外焦平面封装的红外级康宁玻璃基片上进行激光标刻为例，对透明样品进行激光标刻所涉及的一些基本参数，包括烧蚀阈值、激光加工头的光束特性参数以及扫描偏角引起的几何误差等，进行了实际测量和分析，在此基础上得出了合适的打标策略和激光参数，并成功应用于实际操作。此种策略和参数设置方法可以推广到对其他透明材料进行激光标刻。

对于目标的攻击、干扰和探测，超宽带时域脉冲源的幅值直接影响其攻击、干扰和探测的强度和效果。基于雪崩晶体管的Marx电路被广泛应用在产生此类信号源上，传统的Marx电路可以一定程度上提高输出电压的幅值，但由于雪崩晶体管功率容量较低等原因，雪崩晶体管的Marx电路输出电压幅度会随级数增加而达到饱和。针对此类问题，为了产生更高幅值的脉冲信号，综合采用提高触发信号和使用宽带功率合成器的手段。最终利用26级Marx电路作为触发信号，4路40级Marx电路进行功率合成的方法，实现了输出电压幅值为8.7 kV、上升沿约为180 ps的技术指标，并通过机理分析了高触发信号对雪崩晶体管Marx电路的影响，通过实验得到了印证。