使用强场太赫兹泵浦二次谐波产生探测、研究外尔半金属TaAs中的三阶非线性响应过程。当泵浦太赫兹电场沿着TaAs（112）晶面的不同晶向时，强场太赫兹诱导的光学二次谐波信号展现出了不同的响应，这可以用泵浦太赫兹电场引入的三阶非线性极化来定量地解释，其中较大的zzzz分量可能起着重要的作用。

As a newly discovered type of structured light, a spatiotemporal optical vortex (STOV), which is remarkable for its space–time spiral phase and transverse orbital angular momentum (OAM), has garnered substantial interest. Most previous studies have focused on the generation, characterization, and propagation of STOVs, but their nonlinear frequency conversion remains largely unexplored. Here, we experimentally demonstrate the generation of green and ultraviolet (UV) STOVs by frequency upconversion of a STOV carried near-infrared (NIR) pulse emitted by a high repetition rate Yb-doped fiber laser amplifier system. First, we verify that the topological charge of spatiotemporal OAM (ST-OAM) is doubled along with the optical frequency in the second-harmonic generation (SHG) process, which is visualized by the diffraction patterns of the STOVs in the fundamental and second-harmonic field. Second, the space–time characteristic of NIR STOV is successfully mapped to UV STOV by sum-frequency mixing STOV at 1037 nm and Gaussian beams in the green band. Furthermore, we observe the topological charges of the ST-OAM could be degraded owing to strong space–time coupling and complex spatiotemporal astigmatism of such beams. Our results not only deepen our understanding of nonlinear manipulation of ST-OAM spectra and the generation of STOVs at a new shorter wavelength, but also may promote new applications in both classical and quantum optics.

衰老是引起主动脉硬化进而引发各种心血管疾病的主要独立风险因素。对主动脉增龄性改变进行定量评估有望为心血管疾病研究提供重要线索。采用二次谐波成像技术，结合三维灰度共生矩阵纹理分析算法，对不同周龄大鼠主动脉血管壁内外表面的胶原纤维进行了定量评估；提取出多种可量化表征主动脉增龄性改变的特征参数，从胶原纤维微结构角度揭示了主动脉增龄性变化规律。上述方法及提取出的特征参数有望为评估血管老化程度提供有力工具和重要参考指标，并进一步应用于与老化相关的心血管疾病的研究。

面向天文观测等领域对高功率单频589 nm钠导星激光器的应用需求，通过金刚石拉曼谐振及腔内倍频技术结合1 018 nm掺镱光纤激光技术，实现了最高功率16.5 W的连续波单频589 nm钠导星激光器研制。建立外腔拉曼振荡及腔内倍频理论，详细分析谐振腔输出耦合率和倍频晶体相位匹配条件对输出激光功率的影响。激光光谱宽度为16 MHz，光束质量因子为1.05，光光转化效率为20%。

采用自行研制的776.9 nm半导体激光器作为种子源, 经过锥形半导体放大器并整形后得到2.3 W的基频光,再利用Ⅰ类相位匹配的三硼酸锂晶体和蝶形倍频腔产生了388.4 nm紫外连续激光。分析了锥形放大器中热透镜效应对光束质量的影响, 并通过透镜、柱面镜、棱镜对光束进行整形, 提高了倍频腔的输入耦合效率。进一步通过优化倍频腔的束腰尺寸和腔参数, 提高了紫外激光二次谐波的转换效率。最终2.3 W的基频光产生940 mW的紫外倍频光输出, 倍频效率达到41%。

The compact and reliable ultraviolet (UV) source has attracted remarkable attention for its potential use in optical measurement systems, high-density optical storage, and biomedical applications. We demonstrate ultraviolet generation by frequency doubling in a lithium-tantalate-on-insulator (LTOI) microdisk via modal phase matching. The 50-µm-diameter microdisk was milled by a focused ion beam (FIB) and followed by chemo-mechanical polishing (CMP) to smooth the disk surface and edge, and the Q-factor reaches 2.74×105 in the visible band. On-chip UV coherent light with a wavelength of 384.3 nm was achieved, which shows great promise for using LTOIs in integrated ultraviolet source platforms.

A 222 nm all-solid-state far-ultraviolet C (UVC) pulse laser system based on an optical parametric oscillator (OPO) and second-harmonic generation (SHG) using β-Ba2BO4 (BBO) crystals was demonstrated. Pumped by a Nd:Y3Al5O12 laser with a repetition rate of 100 Hz at 355 nm, the maximum signal laser pulse energy of 1.22 mJ at 444 nm wavelength was obtained from the BBO-OPO system, corresponding to a conversion efficiency of 27.9%. The maximum output pulse energy of 164.9 µJ at the 222 nm wavelength was successfully achieved, corresponding to an SHG conversion efficiency of 16.2%. Moreover, the tunable output wavelength of UVC light from 210 nm to 252.5 nm was achieved.

手性二维钙钛矿是一类具有非中心对称结构的低维钙钛矿材料，兼具低维钙钛矿和手性材料的优点，可用于产生非线性光学效应。通过高压技术可以实现低维钙钛矿各种光学性质的调控，然而目前对手性二维钙钛矿高压光学性质，特别是高压下非线性光学效应的研究则鲜有报道。利用金刚石对顶砧技术研究了高压对手性二维钙钛矿材料(R-, S-)ClPEA₂PbI₄的PL光谱、吸收光谱和二次谐波效应的影响。结果表明，随着压强的增大，材料的PL光谱强度先增大到1 GPa的峰值，随后逐渐减弱直至6 GPa左右消失，同时峰值波长507 nm红移到568 nm。高压吸收谱表明手性钙钛矿在6 GPa附近吸收边存在突变。高压下激光二次谐波信号强度随压强的增大而逐渐减小，在6 GPa附近明显减弱。这些结果表明高压是一种调控二维手性钙钛矿光学性质的有效手段，对其未来在发光和近红外频率转换等器件中的应用提供了基础。