We propose a joint look-up-table (LUT)-based nonlinear predistortion and digital resolution enhancement scheme to achieve high-speed and low-cost optical interconnects using low-resolution digital-to-analog converters (DACs). The LUT-based predistortion is employed to mitigate the pattern-dependent effect (PDE) of a semiconductor optical amplifier (SOA), while the digital resolution enhancer (DRE) is utilized to shape the quantization noise, lowering the requirement for the resolution of DAC. We experimentally demonstrate O-band intensity modulation and direct detection (IM/DD) transmission of 124-GBd 4 / 6-level pulse-amplitude modulation ( PAM ) -4 / 6 and 112-GBd PAM-8 signals over a 2-km standard single-mode fiber (SSMF) with 3 / 3.5 / 4-bit DACs. In the case of 40-km SSMF transmission with an SOA-based preamplifier, 124-GBd on-off-keying (OOK)/PAM-3/PAM-4 signals are successfully transmitted with 1.5 / 2 / 3-bit DACs. To the best of our knowledge, we have achieved the highest net data rates of 235.3-Gb / s PAM-4, 289.7-Gb / s PAM-6, and 294.7 Gb / s PAM-8 signals over 2-km SSMF, as well as 117.6-Gb / s OOK, 173.8-Gb / s PAM-3, and -231.8 Gb / s PAM-4 signals over 40-km SSMF, employing low-resolution DACs. The experimental results reveal that the joint LUT-based predistortion and DRE effectively mitigate the PDE and improve the signal-to-quantization noise ratio by shaping the noise. The proposed scheme can provide a powerful solution for low-cost IM/DD optical interconnects beyond 200 Gb / s.

针对TEM喇叭天线终端反射大、低频辐射效率低的问题，对其进行了仿真优化设计。采用时域分析方法，分析了端部加载电阻与背部加载电阻的低频补偿方法，对TEM喇叭天线的尺寸、极板顶角等结构参数进行了优化，采用末端卷边结构，提升了辐射场的峰值场强与脉宽。根据仿真优化结果，研制了长度2.5 m、天线极板间张角45°、天线极板顶角45°的TEM喇叭天线，通过实测验证了仿真结果。结果表明，加载电阻可以有效降低反射，背部加载电阻方式的峰值场强和脉宽比端部加载电阻高，且采用4个电阻并联加载的效果较好；适当增加天线长度、极板顶角以及极板间夹角可以提高天线辐射性能。该研究结果为TEM喇叭天线在辐射式核电磁脉冲试验系统的应用提供了参考。

强电磁脉冲可通过外部线缆耦合进入车辆发动机管理系统(EMS)内，造成发动机管理系统设备干扰甚至损伤，电磁防护组件可为车辆EMS防护设计提供支撑。以车辆EMS为研究对象，综合考虑EMS设备及其外部连接线缆，建立EMS设备电磁仿真模型，对不同长度线缆的端口耦合特性及EMS金属壳体表面感应电流进行了仿真研究。基于防护电路仿真，设计了一种应用于车辆EMS设备的电磁防护组件。仿真结果表明，该防护组件能将5 kV的电磁脉冲限制在最高峰值幅度为18 V以内，防护效能达到48 dB，将其加装于EMS线缆接口处可有效提高强电磁环境下的可靠性，对于车辆平台控制系统的电磁防护设计具有一定的参考意义。

应用三维MC程序和PIC程序，对神光装置辐照下腔体内系统电磁脉冲（SGEMP）模型进行了耦合模拟。在半高宽为2.9 ns、平均能量为10.3 keV的轫致谱X射线点源辐照下，圆柱腔内电场最大值高达2 MV/m，以轴向电场为主；磁场最大值约为0.8×10⁻³ T，以角向磁场为主，电磁场最大值都集中在发射面附近，以脉冲直流场为主，交流辐射场幅度较小，约在kV/m量级。考察了注量对SGEMP效应的影响，注量越高，电场沿轴向变化越快，交流辐射场占比越大。

针对高功率微波在大气传输中可能出现的击穿现象，研究了脉冲序列中首次击穿时的延迟脉冲数，发现其与种子电子、脉冲击穿概率以及微波场强密切相关。研究发现，微波场强可通过作用于种子电子间接影响脉冲击穿概率和延迟脉冲数，由此提出利用延迟脉冲数估计微波击穿临界场强的方法，并定义在脉冲击穿概率大于一定值时的微波临界场强作为击穿阈值。推导了脉冲击穿概率的估计公式，并对估计量的性能进行了分析，随后利用S波段微波大气击穿模拟装置开展了实验验证。实验结果表明，在一定范围内，重复频率微波脉冲击穿延迟脉冲数仅与种子电子产生率和脉宽成反比，能用于估计脉冲击穿概率，进而给出击穿临界场强。

High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated. The active polarization control technology based on the root-mean-square propagation (RMS-prop) algorithm is employed to guarantee a linearly polarized output from the system. A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio (PER) of > 11.4 dB. In addition, the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser. The M² factor of the laser beam at the highest output power is measured to be less than 1.15, indicating a diffraction-limited beam quality. Finally, the amplified laser pulse is temporally compressed to 755 fs with a highest average power of 273.8 W. This is the first time, to the best of our knowledge, that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier.

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.

Here we report on a simple-to-implement and cost-effective approach for laser pulse contrast enhancement, based on the ${\chi}^{(3)}$ nonlinear self-focusing effect. An intentionally induced and gently controlled self-focusing in a thin glass transforms the time-dependent intensity into variation in beam divergence. Followed by a spatial discriminating filter, only the strongly focused fraction traverses the setup, at the expense of efficiency. A numerical model, accounting for the pulse and material parameters via a Gaussian ABCD matrix, provides an estimate for the instantaneous beam waist and transmission efficiency, which enables us to evaluate the resulting contrast enhancement. The estimated contrast enhancement spans between 0.5 and 2.5 orders of magnitude, in conjunction with approximately 25%–90% estimated efficiency, depending on the pulse parameters. In a preliminary experiment we demonstrated the effect with 10s-μJ sub GW regime with approximately 40 $\%$ efficiency and a contrast improvement of more than or equal to 20 dB.