针对微操作与微装配任务对多维大范围精密定位运动的需求，采用粘滑驱动原理并结合压电柔顺机构设计二自由度、大行程、无耦合并联定位平台。利用桥式机构对内置压电驱动器进行位移放大，并与复合解耦结构配合构成二维柔顺驱动机构。交叉滚柱导轨则连接移动台与驱动机构，并通过预紧螺钉调整接触摩擦力，进而获得良好的粘滑运动特性。采用有限元法建立定位平台的静力学模型，并对位移放大倍数、应力和固有频率进行仿真分析。最后，搭建实验测试系统验证定位平台的输出性能。实验结果表明：在扫描驱动模式下，驱动电压为150 V时，平台x和y向的输出位移分别为63.84 μm和62.61 μm，耦合比为0.52%和0.59%，分辨率为6.5 nm和7.2 nm；在步进驱动模式下，驱动电压为120 V时，平台在x和y向的单步位移分别为47.31 μm和47.20 μm，耦合比为0.69%和0.73%，x正向、x反向、y正向和y反向的运动分辨率分别为0.49，0.47，0.47和0.42 μm，最大垂直负载为50 N，设计的压电粘滑定位平台满足所需性能要求。

通过光纤激光光谱合成技术，可以打破单个光纤激光器输出功率受非线性因素制约的限制，实现更高功率的激光输出。通过梳理光谱合成技术的发展历程并分析其现状，对其原理及优劣势进行分析，结合自身研究，设计了一款便携式3路合成系统，通过设计及优化光纤激光器的放大结构，严格把控参与合束的子束光源的质量，将1055、1070和1085 nm三路高功率窄线宽光纤激光进行合束，对合成系统中采用的双色镜进行研究，对其膜系指标进行严格的设计，对高陡度截止滤光膜的设计方法以及制备工艺进行分析，对其热损伤规律及控制技术进行研究，优化整个合成系统，最终实现合成功率9650 W的高功率激光输出，合成效率92%，光束质量M²为1.7，并对未来双色镜光谱合成进行了展望。

提出了一种用于单纵模激光器选模的基于光纤耦合器的光纤复合环腔（CRC）滤波器的仿真方法，利用该方法对两种新型双耦合器双环CRC （DCDR-CRC）滤波器及三耦合器双环CRC （TCDR-CRC）滤波器进行了理论仿真，通过引入游标原理，分析了两种滤波器在不同环长差下的滤波特性，并通过调整DCDR-CRC及TCDR-CRC的耦合比、环长及环长差，对有效自由光谱范围 （FSR）、抑制比 （SR）及主透射峰带宽进行优化，计算结果表明优化后环腔的有效FSR可有效抑制波长选择器传输通带内的增益竞争，较低的SR可以抑制CRC滤波器相邻透射峰之间的增益竞争，较窄的主透射峰可以保证仅有一个激光器的纵模被选择。

The 4H-SiC crystal is found to have great potential in terahertz generation via nonlinear optical frequency conversion due to its extremely high optical damage threshold, wide transparent range, etc. In this paper, optical rectification (OR) with tilted-pulse-front (TPF) setting based on the 4H-SiC crystal is proposed. The theory accounts for the optimization of incident pulse pre-chirping in the TPF OR process under high-intensity femtosecond laser pumping. Compared with the currently recognized LiNbO₃-based TPF OR, which generates a single-cycle terahertz pulse within 3 THz, 4H-SiC demonstrates a significant advantage in producing ultra-widely tunable (up to over 14 THz, TPF angle 31°–38°) terahertz waves with high efficiency (~10^–2) and strong field (~MV/cm). Besides, the spectrum characteristics, as well as the evolution from single- to multi-cycle terahertz pulses can be modulated flexibly by pre-chirping. The simulation results show that 4H-SiC enables terahertz frequency extending to an unprecedent range by OR, which has extremely important potential in strong-field terahertz applications.

Perfect optical vortices (POVs), characterized as a ring radius independent of topological charge (TC), possess extensive application in particle manipulation and optical communication. At present, the complex and bulky optical device for generating POVs has been miniaturized by leveraging the metasurface, and either spin-dependent or spin-independent POV conversions have been further accomplished. Nevertheless, it is still challenging to generate superposed POVs for incidences with orthogonal circular polarization. Here, a spin-multiplexed all-dielectric metasurface method for generating superposed POVs in the terahertz frequency range is proposed and demonstrated. By using the multiple meta-atom comprised structure as the basic unit, the complex amplitude of two superposed POVs is modulated, decoupled, and subsequently encoded to left- and right-handed circular polarization incidences. Furthermore, two kinds of metasurfaces are fabricated and characterized to validate this controlling method. It is demonstrated that the measured intensity and phase distributions match well with the calculation of the Rayleigh–Sommerfeld diffraction integral, and the radius of superposed POVs is independent of TCs. This work provides promising opportunities for developing ultracompact terahertz functional devices applied to complex structured light generation and terahertz communication, and exploring sophisticated spin angular momentum and orbital angular momentum interactions like the photonic spin-Hall effect.

固体材料在超快强激光驱动下的高次谐波辐射是凝聚态物理、材料学、光学与光子学等学科领域的交叉研究方向。目前固体高次谐波研究已经从金属、半导体、普通绝缘体等块体材料拓展到低维纳米结构，并且在拓扑绝缘体和拓扑表面态上也成功探测到非微扰的高次谐波信号。与气相原子、分子相比，固体材料具有更高的原子密度，且固体高次谐波的产生机制更为复杂，在新型光源、材料物性和微观动力学表征等方面拥有良好的应用前景。本文主要回顾了近年来固体高次谐波的实验和理论进展，并对其机制及潜在应用进行探讨和展望。

为推动北京大学超导加速器实验装置不断向强流目标迈进，提出100 W红外高重频光阴极驱动激光的设计方案，主放大器采用先进的光子晶体增益光纤，保证输出光束的质量。对激光系统中的关键问题，如各部分功率指标、脉冲展宽和压缩、激光耦合等进行了设计，并且考虑了激光的非线性影响。为实现强流加速器开机运行所必备的诊断模式，也提出了对于高重频激光进行两级选频的独特设计方案。将高速的SOA光开关和低速的声光调制器相结合，产生宏脉冲结构的输出激光，从而实现加速器在诊断模式下的运行。