Electrochemical reduction of CO2 into high-value hydrocarbons and alcohols by using Cu-based catalysts is a promising and attractive technology for CO2 capture and utilization, resulting from their high catalytic activity and selectivity. The mobility and accessibility of active sites in Cu-based catalysts significantly hinder the development of efficient Cu-based catalysts for CO2 electrochemical reduction reaction (CO2RR). Herein, a facile and effective strategy is developed to engineer accessible and structural stable Cu sites by incorporating single atomic Cu into the nitrogen cavities of the host graphitic carbon nitride (g-C3N4) as the active sites for CO2-to-CH4 conversion in CO2RR. By regulating the coordination and density of Cu sites in g-C3N4, an optimal catalyst corresponding to a one Cu atom in one nitrogen cavity reaches the highest CH4 Faraday efficiency of 49.04% and produces the products with a high CH4/C2H4 ratio over 9. This work provides the first experimental study on g-C3N4-supported single Cu atom catalyst for efficient CH4 production from CO2RR and suggests a principle in designing highly stable and selective high-efficiency Cu-based catalysts for CO2RR by engineering Cu active sites in 2D materials with porous crystal structures.

We investigate the generation of single-transverse-mode Laguerre-Gaussian (LG) emission from a diode-end-pumped Nd:YVO4, 1064 nm laser using mode selection via intracavity spherical aberration (SA). We present both theoretical and experimental investigations, examining the limits of the order (both radial and angular indices) of the LG modes which can be produced, along with the resultant output power. We found that in order to generate single-mode emission of low-order LG modes which have relatively small beam diameters, lenses with shorter focal-length were required (to better differentiate neighboring LG modes via SA). The converse was true of LG modes with high-order. Through appropriate choice of the focal length of the intracavity lens, we were able to generate single-mode, LG0,±m laser output with angular indices m selectable from 1 to 95, as well as those with non-zero radial indices p of up to 4.

电力信息系统数据(尤其是国际业务数据)的安全传输关系着整个电网的安全运行。无条件 安全的量子通信技术可大幅提高系统数据传输的安全级别,并提供对窃听者的可检测性。 基于与测量设备无关量子密钥分配(MDI-QKD)协议,针对国际电力业务数据传输的特殊性, 提出将MDI-QKD协议应用到传统的电力系统国际业务数据传输的即插即用MDI-QKD方案,此方 案包括测量控制中心、外网国际业务专区和海外传输前置区。测量控制中心负责光脉冲的产 生和贝尔态测量,外网国际业务专区和海外传输前置区通过密钥管理端口与量子虚拟专用 网(VPN)相连,实施数据加密,理论分析验证了所提方案的可行性。

分析了传统Pound-Drever-Hall (PDH)激光稳频方法的工作原理，设计了一种基于正交解调原理的PDH 激光稳频方案。该方案采用直接数字频率合成器同时产生两路频率均为10 MHz 的正弦和余弦信号，其中正弦信号分为两路：一路用于驱动电光相位调制器以产生相位边带，另一路与余弦信号一起作为相位解调的参考信号。经相位调制后的激光束耦合进入F-P 参考腔，所产生的光外差干涉信号由光电探测器进行探测，其输出信号分别与两路正交参考信号进行混频，经低通滤波后得到误差信号的两个正交分量，二者经A/D 转换后进入微处理器进行正交相敏检波运算，即可得到PDH 稳频系统的误差信号。建立了正交解调PDH 激光鉴频实验系统，对F-P 参考腔的腔长进行线性扫描，观察到了鉴频曲线，其鉴频灵敏度为1.82 V/MHz，最大频率变化量为5.48 MHz。实验结果表明，所设计的正交解调PDH 稳频方案可行。

为了增强β-FeSi2 薄膜的发光强度，通过脉冲激光轰击(PLD)β-FeSi2和Si靶材沉积于Si(1 1 1)面制备了优质的β-FeSi2/Si薄膜，薄膜表面光滑、平整，β-FeSi2颗粒尺寸在20~50 nm左右。光致发光(PL)测试显示，β-FeSi2/Si薄膜在低温下(20 K)在1540 nm 左右的近红外处有一较强发光峰，对应b-FeSi2带-带跃迁。对Si 层进行掺杂Er3+处理，发现处理后的β-FeSi2/Si∶Er 薄膜发光强度得到明显地增强，掺入Er 使β-FeSi2/Si 薄膜非辐射复合中心得到有效地抑制，且β-FeSi2/Si:Er 薄膜的红外发光来自Er3+离子的4I13/2→4I15/2的跃迁和β-FeSi2纳米颗粒带带复合的发光叠加。

The propagation of picosecond deep ultraviolet laser pulse at wavelength of 193 nm in air is numerically investigated. Long plasma channel can be formed due to the competition between Kerr self-focusing and ionization induced defocusing. The plasma channel with electron density of above 10<sup>13</sup>/cm<sup>3</sup> can be formed over 70 m by 50-ps, 20-mJ laser pulses. The fluctuation of laser intensity and electron density inside ultraviolet (UV) plasma channel is significantly lower than that of infrared pulse. The linear absorption of UV laser by air is considered in the simulation and it is shown that the linear absorption is important for the limit of the length of plasma channel.