激光功率和能量计量技术的现状与展望

功率和能量是激光器的两个基本参数,激光功率和能量测量一直是激光参数计量中最基础的测量工作.总结了美国标准技术研究院(NIST)、英国国家物理实验室(NPL)以及中国国家计量院(NIM)在激光功率能量计量方面的技术现状,重点介绍了国防科工委光学计量一级站激光功率能量计量方面已具备的条件,详细说明了所采用的测量原理以及所达到的测量范围和测量不确定度等技术指标.提出了激光功率和能量计量的发展趋势和发展方向.     

Perturbative Power Counting,Lowest-Index Operators and Their Renormalization in Standard Model Effective Field Theory

We study two aspects of higher dimensional operators in standard model effective field theory.We first introduce a perturbative power counting rule for the entries in the anomalous dimension matrix of operators with equal mass dimension.The power counting is determined by the number of loops and the difference of the indices of the two operators involved,which in turn is defined by assuming that all terms in the standard model Lagrangian have an equal perturbative power.Then we show that the operators with the lowest index are unique at each mass dimension d,i.e.,(H~?H)~(d/2)for even d≥4,and(L~TεH)C(L~TεH)~T(H~?H)~((d-5)/2)for odd d≥5.Here H,L are the Higgs and lepton doublet,andε,C the antisymmetric matrix of rank two and the charge conjugation matrix,respectively.The renormalization group running of these operators can be studied separately from other operators of equal mass dimension at the leading order in power counting.We compute their anomalous dimensions at one loop for general d and find that they are enhanced quadratically in d due to combinatorics.We also make connections with classification of operators in terms of their holomorphic and anti-holomorphic weights.     

10MW串级脉冲发电机的理论、设计、实验及应用研究

 脉冲发电机具有小型、机动、灵活、可靠、寿命长等特点, 作为高功率固体激光器和加速器电源是一新的技术路线。比较了各种类型脉冲电源的性能指标,解释了旋转磁通压缩和串级原理,提出串级脉冲发电机的自激、偏极与双机同壳概念,给出电机的设计公式,10MW串级脉冲发电机的设计、实验及在强激光与粒子束领域中的潜在应用。     

Analysis of the generation mechanism of the S-shaped J—V curves of MoS2/Si-based solar cells

Amorphous-microcrystalline MoS$_{2}$ thin films are fabricated using the sol-gel method to produce MoS$_{2}$/Si-based solar cells. The generation mechanisms of the S-shaped current density-voltage ($J$-$V$) curves of the solar cells are analyzed. To improve the performance of the solar cells and address the problem of the S-shaped $J$-$V$ curve, a MoS$_{2}$ film and a p$^+$ layer are introduced into the front and back interfaces of the solar cell, respectively, which leads to the formation of a p-n junction between the p-Si and the MoS$_{2}$ film as well as ohmic contacts between the MoS$_{2}$ film and the ITO, improving the S-shaped $J$-$V$ curve. As a result of the high doping characteristics and the high work function of the p$^+$ layer, a high-low junction is formed between the p$^+$ and p layers along with ohmic contacts between the p$^+$ layer and the Ag electrode. Consequently, the S-shaped $J$-$V$ curve is eliminated, and a significantly higher current density is achieved at a high voltage. The device exhibits ideal p-n junction rectification characteristics and achieves a high power-conversion efficiency (CE) of 7.55%. The findings of this study may improve the application of MoS$_{2}$ thin films in silicon-based solar cells, which are expected to be widely used in various silicon-based electronic and optical devices.     

Efficient and stable wireless power transfer based on the non-Hermitian physics

As one of the most attractive non-radiative power transfer mechanisms without cables,efficient magnetic resonance wireless power transfer(WPT)in the near field has been extensively developed in recent years,and promoted a variety of practical applications,such as mobile phones,medical implant devices and electric vehicles.However,the physical mechanism behind some key limitations of the resonance WPT,such as frequency splitting and size-dependent efficiency,is not very clear under the widely used circuit model.Here,we review the recently developed efficient and stable resonance WPT based on non-Hermitian physics,which starts from a completely different avenue(utilizing loss and gain)to introduce novel functionalities to the resonance WPT.From the perspective of non-Hermitian photonics,the coherent and incoherent effects compete and coexist in the WPT system,and the weak stable of energy transfer mainly comes from the broken phase associated with the phase transition of parity-time symmetry.Based on this basic physical framework,some optimization schemes are proposed,including using nonlinear effect,using bound states in the continuum,or resorting to the system with high-order parity-time symmetry.Moreover,the combination of non-Hermitian physics and topological photonics in multi-coil system also provides a versatile platform for long-range robust WPT with topological protection.Therefore,the non-Hermitian physics can not only exactly predict the main results of current WPT systems,but also provide new ways to solve the difficulties of previous designs.     

50~250 keV质子入射SiC和Si靶时的电子发射特性研究

在中国科学院近代物理研究所兰州重离子加速器国家实验室测量了能量范围为50~250 keV 的质子入射碳化硅靶和硅靶表面的电子发射产额。实验结果发现,两种半导体靶材的电子发射产额随质子入射能量变化趋势均与作用过程中电子能损随质子入射能量的变化趋势相似。通过分析电子发射的能量来源,发现实验中电子发射产额主要由动能电子发射产额贡献,势能电子发射产额可以忽略不计。两种靶材的电子发射产额均近似地正比于质子入射靶材过程中的电子能损,比例系数B随入射能量略有变化。     

超导电力技术新进展及其未来发展的思考

近年来高温超导材料研究取得很大进展,它在电力领域的应用研究已受到广泛关注,一些示范样机,诸如高温超导输电电缆、变压器、故障电流限制器、电机和储能装置已经研制成功并投入示范性试验.超导技术是21世纪具有战略经济意义的高新技术,文章将介绍高温超导电力应用研究的新进展及其未来发展的思考。     

爆电换能脉冲大电流输出研究

 基于爆电换能原理,使用掺铌的PZT 95/5陶瓷组装换能器件,在垂直工作模式下,对爆电电源LRC电路响应进行了理论分析,并开展了脉冲大电流输出实验研究。实验采用多组PZT 95/5铁电陶瓷并联,利用平面波发生器作为冲击加载手段,获得了峰值5 kA以上的脉冲大电流,初始电流上升速率可达10~20 GA/s。实验结果与理论设计符合较好。     

Short Tm3+-doped fiber lasers with watt-level output near 2 μm

High-power operation of diode-pumped fiber lasers at wavelength near 2μm are demonstrated with short length of heavily Tm3 -doped silica glass fibers. With 7-cm long fiber, a laser at near 2 μm is obtained with the threshold of 135 mW, maximum output power of 1.09 W, and slope efficiency of 9.6% with respect to the launched power from a laser diode at 790 nm. The output stability of this fiber laser is within 5%.The dependence of the performance of fiber lasers on the operation temperature and cavity configuration parameters is also investigated.     

一种大功率窄脉冲半导体激光器测试台的研制

大功率窄脉冲半导体激光器主要光电性能参数为:输出峰值光功率、阈值电流、正向电压、上升时间、峰值波长、光谱半宽、半强度角.根据激光制导系统对大功率窄脉冲激光器参数的特殊测试要求,研制一种大功率窄脉冲激光器测试平台,将小型化大功率激励器功放模块、大范围可调DC-DC模块、信号源板、激光器座、光学准直镜集成在一个平台上,与峰值功率计、光谱仪、CCD摄像机等仪器配合,可测出大功率窄脉冲激光器的峰值功率、峰值波长及波长随温度变化的漂移特性、发光芯均匀性等参数.介绍了大功率窄脉冲激光器测试台的特点,并对测试结果作了论述.