增材制造结合反应烧结技术能够制备高度轻量化的碳化硅陶瓷反射镜，针对增材制造技术制备的碳化硅陶瓷存在抗弯强度低、弹性模量低等力学性能差的问题，开展高温氧化提升材料力学性能的研究。对基于增材制造的反应烧结碳化硅陶瓷试样在850 ℃下进行高温氧化处理，研究氧化时间对材料成分及表面缺陷含量的影响，阐明氧化时间对材料性能的提升机制，揭示它对材料性能的影响规律。实验结果表明：当氧化时间为2 h时，材料表面原位生长一层致密的氧化硅膜层，该膜层能够使材料表面缺陷自愈合，有效降低陶瓷材料表面缺陷的含量，此时材料获得最佳的力学性能，抗弯强度和弹性模量分别为263.9 MPa和384.75 GPa，分别提升10.7%和14.4%。该方法具有高效率、低成本和易操作的优势，为增材制造碳化硅陶瓷的性能优化提供理论指导。

In this paper, the frequency difference of the eigen polarization modes of the Nd:YAG crystal laser at different polarization ratios is experimentally studied, and to the best of our knowledge, the correlation between the frequency difference of the eigenmodes and the output polarization degree is reported for the first time. Combined with the analysis of the polarization beam profile, it is proved that the polarized laser produced by the isotropic crystal is due to the frequency locking of the eigen polarization modes. The weak birefringence in the crystal causes the round-trip phase difference of the orthogonal polarization modes, which leads to the frequency difference between the polarization modes. By the adjustment of the cavity mirror, the anisotropic loss will interact with the round-trip phase difference. The eigen polarization modes can reach frequency degeneration, and then be coherently combined to produce linearly polarized laser output. This work provides a useful reference for understanding the physical mechanism of polarized lasers realized by isotropic crystals.

近年来，将近红外光转换为短波长的可见或近红外光的稀土纳米晶上转换发光研究吸引了生物成像、纳米温度传感、太阳能电池等领域研究者的广泛关注。面向多领域的应用需求，稀土纳米晶上转换发光需提高其发光强度、发光波长以及激发波长的选择性。本文综述了纳米尺度上，通过组成、结构以及核壳结构的设计，在理解上转换发光过程的能量传递路径和上转换发光过程的基础上，提高对上转换发光的颜色、各跃迁的比例以及发光强度、发光寿命等调控的研究进展。此外，还关注了纳米晶与贵金属表面电场、表面有机分子以及环境温度的耦合在提高辐射跃迁几率、减少无辐射能量损失等方面提高其上转换发光强度的研究发展趋势。

1T-polytype tantalum disulfide (1T-TaS2), an emerging strongly correlated material, features a narrow bandgap of 0.2 eV, bridging the gap between zero-bandgap graphene and large-bandgap 2D nonlinear optical (NLO) materials. Combined with its intense light absorption, high carrier concentration, and high mobility, 1T-TaS2 shows considerable potential for applications in broadband optoelectronic devices. However, its NLO characteristics and related applications have rarely been explored. Here, 1T-TaS2 nanosheets are prepared by chemical vapor deposition. The ultrafast carrier dynamics in the 400–1100 nm range and broadband NLO performance in the 515–2500 nm range are systematically studied using femtosecond lasers. An obvious saturable absorption phenomenon is observed in the visible to IR range. The nonlinear absorption coefficient is measured to be -22.60±0.52cmMW-1 under 1030 nm, which is larger than that of other typical 2D saturable absorber (SA) materials (graphene, black phosphorus, and MoS2) under similar experimental conditions. Based on these findings, using 1T-TaS2 as a new SA, passively Q-switched laser operations are successfully performed at 1.06, 1.34, and 1.94 μm. The results highlight the promise of 1T-TaS2 for broadband optical modulators and provide a potential candidate material system for mid-IR nonlinear optical applications.

Different laminated structures of TiO2/SiO2 composite film were prepared via atomic layer deposition (ALD) on alumina substrates. The effect of the annealing temperature in the air on the surface morphologies, crystal structures, binding energies, and ingredient content of these films was investigated using X-ray diffraction, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy. Results showed that the binding energy of Ti and Si increased with decrease of the Ti content, and the TiO2/SiO2 nanolaminated films exhibited a complex bonding structure. As the annealing temperature increased, the thickness of the nanolaminated films decreased, and the density and surface roughness increased. An increase in the crystallization temperature was proportional to the SiO2 content in TiO2/SiO2 composite film. The annealing temperature and thin thickness strongly affected the phase structure of the ALD TiO2 thin film. To be specific, the TiO2 thin film transformed into an anatase phase from an amorphous phase after an increase in the annealing temperature from 400°C to 550°C, and the TiO2 film exhibited an anatase phase until the annealing temperature reached 850°C, owing to its extremely small thickness. The annealing process caused the Al ions in the substrate to diffuse into the films and bond with O.