Surface acoustic wave (SAW) resonators based on lithium tantalate (LT, LiTaO3) wafers are crucial elements of mobile communication filters. The use of intrinsic LT wafers typically brings about low fabrication accuracy of SAW resonators due to strong UV reflection in the lithography process. This hinders their resonance frequency control seriously in industrial manufacture. LT doping and chemical reduction could be applied to decrease the UV reflection of LT wafers for high lithographic precision. However, conventional methods fail to provide a fast and nondestructive approach to identify the UV performance of standard single-side polished LT wafers for high-precision frequency control. Here, we propose a convenient on-line sensing scheme based on the colorimetry of reduced Fe-doped LT wafers and build up an automatic testing system for industrial applications. The levels of Fe doping and chemical reduction are evaluated by the lightness and color difference of LT-based wafers. The correlation between the wafer visible colorimetry and UV reflection is established to refine the lithography process and specifically manipulate the frequency performance of SAW resonators. Our study provides a powerful tool for the fabrication control of SAW resonators and will inspire more applications on sophisticated devices of mobile communication.

The laser-induced damage threshold (LIDT) of plate laser beam splitter (PLBS) coatings is closely related to the subsurface absorption defects of the substrate. Herein, a two-step deposition temperature method is proposed to understand the effect of substrate subsurface impurity defects on the LIDT of PLBS coatings. Firstly, BK7 substrates are heat-treated at three different temperatures. The surface morphology and subsurface impurity defect distribution of the substrate before and after the heat treatment are compared. Then, a PLBS coating consisting of alternating HfO₂–Al₂O₃ mixture and SiO₂ layers is designed to achieve a beam-splitting ratio (transmittance to reflectance, s-polarized light) of approximately 50:50 at 1053 nm and an angle of incidence of 45°, and it is prepared under four different deposition processes. The experimental and simulation results show that the subsurface impurity defects of the substrate migrate to the surface and accumulate on the surface during the heat treatment, and become absorption defect sources or nodule defect seeds in the coating, reducing the LIDT of the coating. The higher the heat treatment temperature, the more evident the migration and accumulation of impurity defects. A lower deposition temperature (at which the coating can be fully oxidized) helps to improve the LIDT of the PLBS coating. When the deposition temperature is 140°C, the LIDT (s-polarized light, wavelength: 1064 nm, pulse width: 9 ns, incident angle: 45°) of the PLBS coating is 26.2 J/cm², which is approximately 6.7 times that of the PLBS coating deposited at 200°C. We believe that the investigation into the laser damage mechanism of PLBS coatings will help to improve the LIDT of coatings with partial or high transmittance at laser wavelengths.

我国风云四号A星（FY-4A）携带高光谱红外干涉式大气探测仪（Geostationary Interferometric Infrared Sounder，GIIRS）首次实现了地球静止轨道红外高光谱探测，可连续获得大气温湿度廓线信息。基于常规无线电探空资料，从产品的探测能力和精度方面对2020年FY-4A/GIIRS大气温度廓线产品开展质量评估，为产品应用和算法研究提供参考。结果表明：FY-4A/GIIRS反演大气温度廓线探测能力在高度层次和月份统计上受云活跃度影响较大；晴空条件下大气整层均方根误差约为2 K，700~1 000 hPa的大气低层较大，约2.5 K，偏差整层以负值为主；月尺度质量评估可见夏秋两季明显优于冬春季，有利于灾害性天气多发季节的监测；有云条件下单个像元的温度廓线误差显著增大，采用多像元Cressman客观分析可有效提高产品可用性；低海拔地区温度廓线产品质量整体优于高海拔地区，可极大地弥补我国东部、南部地区以及广阔的洋面上的探空资料的不足。

In this study, a toroidal quartz ( $20\overline{2}3$ ) crystal is designed for monochromatic X-ray imaging at 72.3°. The designed crystal produces excellent images of a laser-produced plasma emitting He-like Ti X-rays at 4.75 keV. Based on the simulations, the imaging resolutions of the spherical and toroidal crystals in the sagittal direction are found to be 15 and 5 μm, respectively. Moreover, the simulation results show that a higher resolution image of the source can be obtained by using a toroidal crystal. An X-ray backlight imaging experiment is conducted using 4.75 keV He-like Ti X-rays, a 3 × 3 metal grid, an imaging plate and a toroidal quartz crystal with a lattice constant of 2d = 0.2749 nm. The meridional and sagittal radii of the toroidal α-quartz crystal are 295.6 and 268.5 mm, respectively. A highly resolved image of the microgrid, with a spatial resolution of 10 μm, is obtained in the experiment. By using similar toroidal crystal designs, the application of a spatially resolved spectrometer with high-resolution X-ray imaging ability is capable of providing imaging data with the same magnification ratio in the sagittal and meridional planes.

Various coatings in high-power laser facilities suffer from laser damage due to nodule defects. We propose a nodule dome removal (NDR) strategy to eliminate unwanted localized electric-field (E-field) enhancement caused by nodule defects, thereby improving the laser-induced damage threshold (LIDT) of laser coatings. It is theoretically demonstrated that the proposed NDR strategy can reduce the localized E-field enhancement of nodules in mirror coatings, polarizer coatings and beam splitter coatings. An ultraviolet (UV) mirror coating is experimentally demonstrated using the NDR strategy. The LIDT is improved to about 1.9 and 2.2 times for the UV mirror coating without artificial nodules and the UV mirror coating with artificial nodule seeds with a diameter of 1000 nm, respectively. The NDR strategy, applicable to coatings prepared by different deposition methods, improves the LIDT of laser coating without affecting other properties, such as the spectrum, stress and surface roughness, indicating its broad applicability in high-LIDT laser coatings.

当前基于卷积神经网络的光学遥感图像场景分类方法大多是全局特征学习，忽略了场景局部特征，从而难以较好地解决类内差异大和类间相似性高的问题，因此，提出一种基于视觉转换器和图卷积网络双分支结构的光学遥感图像场景分类方法。该方法首先对场景图像进行分块，再利用位置编码和视觉转换器进行特征编码，从而挖掘图像内部的长距离依赖关系。另一方面，对遥感图像进行超像素分割，将每个超像素对应的卷积神经网络特征进行池化处理并作为图结构中的结点，利用图卷积网络对场景内部图结构进行建模，感知场景内部的空间拓扑关系。最终融合两个分支产生的特征形成场景内容的最终特征表示并用于分类。在光学遥感图像数据集上的实验验证了所提方法在遥感场景分类中的有效性。

In spectral diagnostic physics experiments of inertial confinement fusion, the spectral signal is weak due to the low diffraction efficiency when using bent crystals. A spectral diagnostic instrument with high efficiency and wide spectral range is urgently needed. A multi-curvature bent crystal with multi-energy focusing ability is proposed based on the traditional conical crystal geometry. It has advantages of wide spectral range, strong focusing ability, and high spectral resolution. It also can eliminate the imaging aberration in principle due to rotational symmetry for the incoming X rays. A spectral diagnostic experiment based on a fabricated multi-curvature α-quartz crystal was accomplished using a titanium X-ray tube of the bent crystal, and the corresponding experimental data using a plane α-quartz crystal was also acquired to demonstrate the strong focusing ability. The result shows that the Kα intensity of the multi-curvature α-quartz crystal is 157 times greater than that of the plane crystal, and the corresponding energy range is about 4.51–5.14 keV. This diagnostic instrument could be combined with a streak camera at a vertical direction so as to intensify the diffracted X-ray signal with a wide spectral range.