The development of semiconductors is always accompanied by the progress in controllable doping techniques. Taking AlGaN-based ultraviolet (UV) emitters as an example, despite a peak wall-plug efficiency of 15.3% at the wavelength of 275 nm, there is still a huge gap in comparison with GaN-based visible light-emitting diodes (LEDs), mainly attributed to the inefficient doping of AlGaN with increase of the Al composition. First, p-doping of Al-rich AlGaN is a long-standing challenge and the low hole concentration seriously restricts the carrier injection efficiency. Although p-GaN cladding layers are widely adopted as a compromise, the high injection barrier of holes as well as the inevitable loss of light extraction cannot be neglected. While in terms of n-doping the main issue is the degradation of the electrical property when the Al composition exceeds 80%, resulting in a low electrical efficiency in sub-250 nm UV-LEDs. This review summarizes the recent advances and outlines the major challenges in the efficient doping of Al-rich AlGaN, meanwhile the corresponding approaches pursued to overcome the doping issues are discussed in detail.

采用金属有机化学气相沉积（MOCVD）工艺在p-GaAs（100）衬底上外延了Ga₂O₃薄膜并制备了n-Ga₂O₃/p-GaAs异质结日盲紫外探测器。通过X射线衍射仪、原子力显微镜、场发射扫描电子显微镜等方法对Ga₂O₃薄膜表面形貌、晶体质量进行了测试与分析。结果表明，Ga₂O₃薄膜呈单一晶向，薄膜表面平整且为Volmer-Weber模式外延。测试表明，n-Ga₂O₃/p-GaAs异质结探测器具有明显的整流特性。器件在5 V反向偏压和紫外光（254 nm）照射下实现了超过3.0×10⁴的光暗电流比、7.0 A/W的响应度、3412%的外量子效率、4.6×10¹³ Jones的探测率。我们利用TCAD软件对器件结构进行仿真，得到了器件内的电场分布和能带结构，并分析了器件的工作原理。该异质结探测器性能较好，制造工艺简单，为Ga₂O₃超灵敏日盲紫外探测器的研制提供了新途径。

液晶空间光调制器通过改变驱动电压强度控制液晶分子排布实现对光的调制。紫外区域可用的液晶空间光调制器随光聚合式3D打印等应用的兴起，重要性日益显现。然而绝大多数液晶材料都是有机物，在紫外波段存在光吸收和光反应。为了拓宽液晶材料的应用波段，本文通过选择在应用波段不发生紫外吸收和光反应的官能团，设计了一类可在325~400 nm波段应用不发生光吸收和光反应的液晶材料，并对液晶材料的紫外-可见光光谱进行仿真以验证设计的合理性。将耐紫外液晶化合物配置成混合液晶材料后与常见的两种混合液晶材料的紫外稳定性进行比较。在经过120 min的325 nm紫外光源的辐照后，液晶材料的吸光度和相变温度几乎不变，双折射率变化0.04%，阈值电压变化1.39%，响应时间变化0.32%。

We report a high-stability ultrafast ultraviolet (UV) laser source at 352 nm by exploring an all-fiber, all-polarization-maintaining (all-PM), Yb-doped femtosecond fiber laser at 1060 nm. The output power, pulse width, and optical spectrum width of the fiber laser are 6 W, 244 fs, and 17.5 nm, respectively. The UV ultrashort pulses at a repetition rate of 28.9 MHz are generated by leveraging single-pass second-harmonic generation in a 1.3-mm-long BiB₃O₆ (BIBO) and sum frequency generation in a 5.1-mm-long BIBO. The maximum UV output power is 596 mW. The root mean square error of the output power of UV pulses is 0.54%. This laser, with promising stability, is expected to be a nice source for frontier applications in the UV wavelength window.