The use of broadband laser technology is a novel approach for inhibiting processes related to laser plasma interactions (LPIs). In this study, several preliminary experiments into broadband-laser-driven LPIs are carried out using a newly established hundreds-of-joules broadband second-harmonic-generation laser facility. Through direct comparison with LPI results for a traditional narrowband laser, the actual LPI-suppression effect of the broadband laser is shown. The broadband laser had a clear suppressive effect on both back-stimulated Raman scattering and back-stimulated Brillouin scattering at laser intensities below 1 × 10¹⁵ W cm^-2. An abnormal hot-electron phenomenon is also investigated, using targets of different thicknesses.

激光驱动惯性约束聚变的打靶过程中，光场不同空间频率的不均匀性会引起内爆的流体力学不稳定性、印痕效应和激光等离子体不稳定性。这些不稳定过程将最终影响内爆压缩倍率，从而影响到点火。为了控制焦斑不均匀性进而抑制不稳定过程，人们提出了束匀滑技术：通过光场调控控制焦斑分布特性，进而控制束靶耦合过程。束匀滑可分为空间域匀滑和时间域匀滑。空间域匀滑通过控制波前形态获得平整的焦斑包络，降低低频不均匀性。时间域匀滑通过控制光束的相干性减弱激光焦斑中的散斑，进而减弱中高频不均匀性。随着抑制更高激光功率密度条件下激光等离子体相互作用的需求愈发紧迫，涌现出一些新型的束匀滑方法。文中介绍了束匀滑技术在大型激光装置上的使用情况，并对目前提出的各种束匀滑技术进行了总结和分析。

低时间相干脉冲可有效提高激光与等离子相互作用中参量不稳定性的阈值，但高效频率转换难题是实现其工程应用瓶颈之一。系统分析了高功率激光驱动器已有的各类低时间相干脉冲频率转换技术的特性，并基于数值模拟和实验分析了部分掺氘DKDP晶体用于超辐射光倍频、三倍频的特性与工程应用可行性，结果表明掺氘17%左右DKDP晶体可以提高钕玻璃系统超辐射光的倍频效率，理论转换效率可达到约80%，10%梯度掺氘DKDP晶体则可实现5 THz带宽三倍频输出。

The use of low-coherence light is expected to be one of the effective ways to suppress or even eliminate the laser–plasma instabilities that arise in attempts to achieve inertial confinement fusion. In this paper, a review of low-coherence high-power laser drivers and related key techniques is first presented. Work at typical low-coherence laser facilities, including Gekko XII, PHEBUS, Pharos III, and Kanal-2 is described. The many key techniques that are used in the research and development of low-coherence laser drivers are described and analyzed, including low-coherence source generation, amplification, harmonic conversion, and beam smoothing of low-coherence light. Then, recent progress achieved by our group in research on a broadband low-coherence laser driver is presented. During the development of our low-coherence high-power laser facility, we have proposed and implemented many key techniques for working with low-coherence light, including source generation, efficient amplification and propagation, harmonic conversion, beam smoothing, and precise beam control. Based on a series of technological breakthroughs, a kilojoule low-coherence laser driver named Kunwu with a coherence time of only 300 fs has been built, and the first round of physical experiments has been completed. This high-power laser facility provides not only a demonstration and verification platform for key techniques and system integration of a low-coherence laser driver, but also a new type of experimental platform for research into, for example, high-energy-density physics and, in particular, laser–plasma interactions.

激光等离子体相互作用的不稳定性将有望通过降低高功率激光装置输出光束的相干性得到大幅缓解。利用低相干光源作为种子源，采用钕玻璃放大介质，研制成功国际首台kJ级大带宽低相干激光装置，实现了带宽13 nm、能量960 J、脉宽3～10 ns可调，相干时间仅为300 fs的大能量光脉冲输出。输出脉冲光谱匀滑无纵模结构，且谱相位随机分布，可实现脉冲波形和光谱分布的无关联精密调控。该装置不仅成功演示验证了低相干激光驱动器的单元技术及系统集成技术，同时也为激光等离子体相互作用及高能量密度物理研究提供了全新的实验研究平台。

In high power laser facility for inertial confinement fusion research, final optics assembly (FOA) plays a critical role in the frequency conversion, beam focusing, color separation, beam sampling and debris shielding. The design and performance of FOA in SG-II Upgrade laser facility are mainly introduced here. Due to the limited space and short focal length, a coaxial aspheric wedged focus lens is designed and applied in the FOA configuration. Then the ghost image analysis, the focus characteristic analysis, the B integral control design and the optomechanical design are carried out in the FOA design phase. In order to ensure the FOA performance, two key technologies are developed including measurement and adjustment technique of the wedged focus lens and the stray light management technique based on ground glass. Experimental results show that the design specifications including laser fluence, frequency conversion efficiency and perforation efficiency of the focus spot have been achieved, which meet the requirements of physical experiments well.

The Shen-Guang II Upgrade (SG-II-U) laser facility consists of eight high-power nanosecond laser beams and one short-pulse picosecond petawatt laser. It is designed for the study of inertial confinement fusion (ICF), especially for conducting fast ignition (FI) research in China and other basic science experiments. To perform FI successfully with hohlraum targets containing a golden cone, the long-pulse beam and cylindrical hohlraum as well as the short-pulse beam and cone target alignment must satisfy tight specifications (30 and $20~\unicode[STIX]{x03BC}\text{m}$ rms for each case). To explore new ICF ignition targets with six laser entrance holes (LEHs), a rotation sensor was adapted to meet the requirements of a three-dimensional target and correct beam alignment. In this paper, the strategy for aligning the nanosecond beam based on target alignment sensor (TAS) is introduced and improved to meet requirements of the picosecond lasers and the new six LEHs hohlraum targets in the SG-II-U facility. The expected performance of the alignment system is presented, and the alignment error is also discussed.