Spatially twisted light with femtosecond temporal structure is of particular interest in strong-field physics and light–matter interactions. However, present femtosecond vortex sources exhibit limited power handling capabilities, and their amplification remains an ongoing challenge particularly for high-order orbital angular momentum (OAM) states due to several inherent technical difficulties. Here, we exploit a straightforward approach to directly amplify a femtosecond optical vortex (FOV, OAM=-8ℏ) by using a two-stage single-crystal fiber (SCF) amplifier system without pulse stretching and compression in the time domain, delivering 23-W, 163-fs pulses at a repetition rate of 1 MHz. The spatial and temporal features are well-conserved during the amplification, as well as the high modal purity (>96%). The results indicate that the multi-stage SCF amplifier system is particularly suited for direct amplification of high-order FOVs. The generated high-power femtosecond OAM laser beams are expected to help reveal complex physical phenomena in light–matter interactions and pave the way for practical applications in attoscience, laser plasma acceleration, and high-dimension micromachining.

针对实测红外图像数据集构建难度大、测试制作成本高的问题，本文提出了一种非成对训练样本条件下的生成对抗网络VTIGAN，实现不同场景下可见光到红外（Visible-to-Infrared，VTI）的高质量图像转换。VTIGAN在transformer模块基础引入了一个新的生成器学习图像内容映射关系，通过重组目标风格特性实现图像风格转换，同时使用PathGAN作为判别器强化模型的图像细节信息生成能力，最后联合对抗损失、多层对比损失、风格相似性损失、同一性损失四种损失函数对模型训练过程进行约束。将VTIGAN与其他主流算法在可见光-红外数据集上进行了广泛的对比实验，同时使用峰值信噪比、结构相似度和Frechét inception distance 3个评价指标进行定量评估和主观定性评价。实验结果表明，VTIGAN相比于次优的UGATIT算法在PSNR，SSIM和FID三个指标上分别提升了3.1%，2.8%和11.3%，有效实现了非成对训练样本条件下可见光到红外的图像转换，且对于复杂场景的抗干扰能力更强，生成的红外图像清晰度高、细节特征完整、真实感强。

从强流脉冲电子直线感应加速器电子束流位置探测器测量原理出发，进行了标定装置物理设计，确定标定装置采用同轴结构，对束流探测器位置测量精度和测量范围、偏心同轴线对位置标定结果的影响进行了理论分析，并根据分析结果确定同轴结构内外导体相对位置调节范围、同轴线长度和特性阻抗。电路模拟和实验测量结果验证了在非匹配传输条件下可以得到满足位置标定要求的快脉冲信号波形。

The emission wavelength of InGaN/GaN dot-in-wire LED can be tuned by modifying the nanowire diameter, but it causes mismatched angular distributions between blue, green, and red nanowires because of the excitation of different waveguide modes. Besides, the far-field radiation patterns and light extraction efficiency are typically calculated by center dipoles, which fails to provide accurate results. To address these issues, we first compare the simulation results between central dipole and dipole cloud with experimental data. Next, we calculate and analyze the display metrics for full-color nanowire LEDs by 3D dipole cloud. Finally, we achieve unnoticeable angular color shift within ±20° viewing cone for augmented reality (AR) and virtual reality (VR) displays with an improved light extraction efficiency.The emission wavelength of InGaN/GaN dot-in-wire LED can be tuned by modifying the nanowire diameter, but it causes mismatched angular distributions between blue, green, and red nanowires because of the excitation of different waveguide modes. Besides, the far-field radiation patterns and light extraction efficiency are typically calculated by center dipoles, which fails to provide accurate results. To address these issues, we first compare the simulation results between central dipole and dipole cloud with experimental data. Next, we calculate and analyze the display metrics for full-color nanowire LEDs by 3D dipole cloud. Finally, we achieve unnoticeable angular color shift within ±20° viewing cone for augmented reality (AR) and virtual reality (VR) displays with an improved light extraction efficiency.