With the increasing power of fiber lasers, single chirped and tilted fiber Bragg gratings (CTFBGs) cannot completely mitigate continuously enhanced system-excited stimulated Raman scattering (SRS). Although improving the loss rate of a single CTFBG or cascading multiple CTFBGs can provide better suppression of the stronger SRS, excessive insertion loss may cause significant attenuation of the output power. Confronting the challenge, we firstly present an SRS mitigation method based on a dual-structure fiber grating in this paper. The dual-structure fiber grating comprises a CTFBG and a fiber Bragg grating structure, which were designed and fabricated on a passive 25/400 double-clad fiber. To evaluate the performance of the grating, a 3 kW fiber master oscillator power amplifier laser is established. The experimental results demonstrate that the SRS mitigation rate of the grating is greater than 30 dB (99.9%), whereas the insertion loss is only approximately 3%, thus allowing for minimal deterioration of the output power. This solves the contradiction between high suppression rate and high insertion loss faced by CTFBGs, which in turn makes dual-structure fiber gratings particularly suitable for mitigating SRS in 3–5 kW high-power fiber lasers.

Four-channel off-axis holography is proposed to simultaneously understand the polarization states and the mode coefficients of linearly polarized (LP) modes in few-mode fiber. Far-field off-axis holograms in the four polarization directions of the fiber laser were acquired at the same moment through a four-channel holographic device. The weights, the relative phase differences, and the polarization parameters of the vector fiber laser mode can be solved simultaneously. The simulated and experimental mode analysis of the laser output by 1060-XP fiber with 6 LP modes at 632.8 nm is conducted, which shows that the similarity of the total intensity distribution of the laser before and after mode analysis is above 0.97. The mode polarization states, the mode weights, and the relative phase differences of the few-mode laser can be determined simultaneously in a single shot by four-channel off-axis holography.

目前光纤光栅在高功率连续光纤激光器中的应用主要有两个方面，一是作为谐振腔腔镜，二是用来抑制激光器的非线性效应。首先论述了光纤光栅作为腔镜技术的发展现状，然后着重论述了能够抑制光纤激光器中非线性效应的特殊光纤光栅的发展状况。并详细描述了倾斜布拉格光纤光栅抑制受激拉曼散射和受激布里渊散射、长周期光纤光栅抑制受激拉曼散射以及相移长周期光纤光栅抑制自相位调制或四波混频等非线性效应引起的光谱展宽的研究进展。最后展望了光纤光栅在高功率光纤激光器领域的发展趋势，认为光纤光栅将朝着更高承载功率与长波长方向发展，同时认为基于飞秒激光刻写的光纤光栅技术、能够同时抑制多种非线性效应的光纤光栅技术、以及基于光纤光栅的光纤激光器激光偏振控制技术等将成为新的研究热点。

传统病理学检测中，由于复杂的染色流程和单一的观察形式等限制着病情的诊断速度，而染色过程实质上是将颜色信息与形态特征关联，效果等同于现代数字技术的生物医学图像的图义分割，这使得研究者们可以通过计算后处理的方式，大大降低生物医学成像处理样品的步骤，实现与传统医学染色金标准一致的成像效果。近些年人工智能深度学习领域的发展促成了计算机辅助分析领域与临床医疗的有效结合，人工智能色彩迁移技术在生物医学成像分析上也逐渐表现出较高的发展潜力。文中回顾了深度学习色彩迁移的技术原理，列举此类技术在生物医学成像领域中的部分应用，并展望了人工智能色彩迁移在生物医学成像领域的研究现状和可能的发展趋势。

激光光闸可以将光纤激光器输出的单束激光通过多通道输出，实现激光器的“一机多用”，是现代化激光智能制造的关键性器件。由于光闸承载功率高达上万瓦，其耦合系统极易产生热效应，影响光闸使用性能。为解决万瓦级激光光闸热效应有效控制的难题，保证光闸的高效耦合与高质量光束输出，采用有限元分析法研究了光闸耦合系统的热效应物理机制，并提出一种基于水循环绕流冷却对光闸耦合系统进行热量管控的新方法。通过万瓦激光下的一系列实验验证，表明文中提出的热效应处理方法保证下，高功率激光光闸能长时间承载万瓦级功率，并保持98%以上的耦合效率，同时抑制了系统的热像差，保证了光闸输出激光的光束质量稳定性。该研究为高功率激光系统的热效应分析及处理提供了有效的手段。

Suppressing nonlinear effects in high-power fiber lasers based on fiber gratings has become a hotspot. At present, research is mainly focused on suppressing stimulated Raman scattering in a high-power fiber laser. However, the suppression of spectral broadening, caused by self-phase modulation or four-wave mixing, is still a challenging attribute to the close distance between the broadened laser and signal laser. If using a traditional fiber grating with only one stopband to suppress the spectral broadening, the signal power will be stripped simultaneously. Confronting this challenge, we propose a novel method based on phase-shifted long-period fiber grating (PS-LPFG) to suppress spectral broadening in a high-power fiber master oscillator power amplifier (MOPA) laser system in this paper. A PS-LPFG is designed and fabricated on 10/130 passive fiber utilizing a point-by-point scanning technique. The resonant wavelength of the fabricated PS-LPFG is 1080 nm, the full width at half maximum of the passband is 5.48 nm, and stopband extinction exceeds 90%. To evaluate the performance of the PS-LPFG, the grating is inserted into the seed of a kilowatt-level continuous-wave MOPA system. Experiment results show that the 30 dB linewidth of the output spectrum is narrowed by approximately 37.97%, providing an effective and flexible way for optimizing the output linewidth of high-power fiber MOPA laser systems.

在高功率光纤激光器反向泵浦信号合束器的制作过程中，经熔融拉锥后输出端的信号光纤纤芯变细，在与输入端信号光纤熔接时产生模场失配问题，造成反向泵浦信号合束器的信号光传输效率降低。针对这一问题，文中搭建了信号光纤熔接的芯径失配功率损耗模型，简析了光纤熔接时芯径失配与信号光功率损耗的关系。设计了一套泵浦信号反向合束器信号光功率损耗测试系统。提出了一种通过优化反向合束器信号光纤参数，提升反向泵浦信号合束器的信号光功率传输效率的方法，并通过预拉锥工艺，制作出一支25/400 （6+1）×1反向合束器，经测试，信号光传输效率优于98%，实验室使用该反向合束器搭建了一台MOPA结构光纤激光放大器，实现了3 kW稳定输出。