利用飞秒激光脉冲整形进行太赫兹波整形

产生太赫兹的一般方法是用超短激光脉冲照射光导天线或半导体材料,产生的太赫兹脉冲形状一般比较复杂.如果要将太赫兹辐射应用于通讯,或者分子反应动力学过程的相关控制,需要能够产生任意形状的太赫兹脉冲.介绍了利用激光脉冲整形对太赫兹波整形的原理和实验研究进展,通过对激发太赫兹辐射的飞秒激光脉冲整形,可以实现对太赫兹波形的控制.控制激励脉冲序列的脉冲间隔可以改变太赫兹脉冲系列的相位关系,调制激光脉冲强度可以产生相应的二进制太赫兹脉冲编码,用周期可变的相位掩模板对飞秒激光脉冲整形实现可调谐窄带太赫兹辐射.     

阿秒科学前沿开拓与强场量子相干控制研究

该研究产生更短脉宽、更高光子能量与更高亮度的阿秒相干光源以及原子分子中阿秒电子波包的探测和控制,预期目标主要包括:(1)实现亚飞秒时间尺度和原子级空间尺度内实时观测和控制电子动力学行为;(2)在多电子弛豫过程中,电子重排、电子-电子碰撞动力学等多电子复杂动力学研究中取得若干突破;(3)揭示有重要意义的化学反应的电子动力学物理本质。探索阿秒脉冲作用下物质的电子动力学新规律及其应用。开展中红外激光与气体介质相互作用产生高次谐波的实验和理论研究,采用双色场方法获得高次谐波连续谱,为进一步将阿秒脉冲宽度测量和光子能量推进到"水窗"做准备。从理论上深入了解分子结构和反应通道和分子高次谐波之间的联系,以及和激光参数之间的关系,为实验研究做准备。获得了一些系列研究成果,包括发现太赫兹辐射波形可以通过改变驱动激光脉冲的CEP而实现控制,在光丝等离子体中太赫兹辐射发生极性反转,利用周期量级极端超快激光脉冲光场自身的不对称性获得增强的太赫兹辐射;发现基于独立电子近似的遂穿模型不能解释次序双电离中的许多现象等。     

基于微型谐振腔的史密斯-帕赛尔自由电子激光

研究了一种由电子枪、微谐振腔、金属光栅和集电极组成的新型史密斯-帕赛尔自由电子激光.利用PIC三维模拟,讨论了该装置的特点.发现在合理的电子能量和光栅参数下,该装置可以产生THz频率范围内的相干高功率脉冲SPR.研究结果表明,当电子束能量E=50keV,电子束电流I=10A时,光栅周期L=0.3mm时,可以得到功率在4 000W左右、脉冲为0.25ns的514.643GHz的太赫兹辐射.     

基于激光等离子体的太赫兹脉冲驱动电子偏转

传统电子加速装置以射频场作为驱动场.相比之下,太赫兹辐射波长更短,加速梯度更高,是未来紧凑型电子加速装置的一种潜在驱动场.此外,太赫兹脉冲可以提供一个超快调制场用于压缩和测量电子脉宽.近年来,太赫兹场与电子的相互作用引起了广泛关注.强激光与等离子体相互作用可同时产生大能量的太赫兹脉冲和大电量的超短电子束,这一优势使其有望成为太赫兹场调控电子、太赫兹泵浦-电子探测的新型独特平台.本文以一种可行的实验布局为例,研究了激光等离子体产生的太赫兹脉冲对同向传播电子束的偏转作用.通过计算模拟,系统讨论了各参数对太赫兹场引起的电子偏转的影响,发现太赫兹电场强度或脉宽增加会使偏转现象更为显著,另外,偏转现象与太赫兹波形有关.初步的演示性实验定性验证了数值分析结果.     

太赫兹时域脉冲成像的三维重建

太赫兹(Terahertz)脉冲成像技术是太赫兹科学与技术中的重要应用领域。飞秒激光的发展使得光导天线成为稳定、可靠的太赫兹脉冲辐射源,为太赫兹成像技术奠定了较好的基础。该文基于Matlab软件,以太赫兹时域脉冲三维成像算法及应用为中心,研究太赫兹脉冲扫描成像数据处理算法,通过对太赫兹反射成像时域脉冲波形的特定参数和峰位时间延迟进行处理,尝试实现三维成像;同时利用Matlab的GUI界面设计太赫兹脉冲成像数据分析平台,对实验数据进行分析验证。     

Nd:La0.02Lu0.98VO4晶体的生长与性能研究

利用提拉法生长Nd:La_(0.02)Lu_(0.98)VO_4单晶.经测试,晶体的晶胞参数a=b=0.703 7 nm,c=0.624 2 nm;a向和c向的热膨胀系数分别为α_a=4.3×10~(-6)K~(-1)和α_c=11.6×10~(-6)K~(-1).室温下测试偏振吸收和荧光光谱,结果显示:晶体在809 nm处有较大的吸收线宽5.00 nm(σ)和6.15 nm(π),较大的吸收截面4.70×10~(-20)cm~2(σ)和10.47×10~(-20)cm~2(π).在1 065 nm处有强荧光发射峰,半峰宽分别为2.27 nm(σ)和1.82 nm(π),受激发射截面σe分别为6.5×10-19cm2(σ)和13.8×10~(-19)cm~2(π),荧光寿命为102.5μs.利用未镀膜的晶片进行初步激光实验,获得1 065 nm连续和调Q激光输出.在最高泵浦功率20 W时,获得最高4.95 W的连续输出,光-光转换效率为24.8%,斜效率27.9%;在脉冲重复频率为5 kHz时,得到最高的峰值功率为61.99 kW.结果表明,Nd:La_(0.02)Lu_(0.98)VO_4晶体可能成为新的脉冲激光晶体.     

基于光电流模型的液体介质太赫兹辐射的理论研究

目的 超快激光作用液体介质相较于与气态、固态介质可产生更高能量的太赫兹波,相关研究工作在实验方面已相对完善,而理论方面缺少完整解释过程,运用逐步建立瞬态光电流模型的进程详尽论述其物理机制,并通过此模型研究水、丙酮等4种溶液在不同参数条件下对太赫兹的转化效率。方法 以水分子为例,在传统光电流模型的基础上,基于其电离原理构建三能级系统,通过水分子电离势确定电离弛豫时间,并联立分子驰豫时间与三阶非线性极化率来确定水分子电离率及电流强度,进而构建完整的液态溶液瞬态光电流模型,并运用该模型在两束800 nm高斯光场下,研究了在水与丙酮等4种液体中不同激光参数对太赫兹辐射能量的影响。结果 电场强度越强,导致的分子电离率越高,对应的太赫兹转换效率也越高,并且在特定的激光强度下,最强太赫兹辐射能量对应一个最佳脉宽及脉冲延迟,处于亚皮秒量级,此外,进一步对比了水和丙酮溶液中,太赫兹辐射的能量差异和时频谱特征,结果表明丙酮辐射产率始终最高。结论 在液体介质中,太赫兹辐射的能量受介质电离势、吸收系数、分子密度等多方面影响,这也同样说明和验证了丙酮综合性能参数优于水、重水和乙醇。利用光电流模型研究不同液态中太...     

半导体超晶格高频放大效应的研究

在直流电场和太赫兹频率交流光电场下,通过弛豫时间近似下半经典的玻尔兹曼输运理论研究了半导体超晶格微带电子的高频响应及太赫兹激光辐射的产生和放大可行性,并发现在微带中布拉格反射导致的高频放大共振可以利用交流的探测激光场观察到.     

太赫兹单光子探测器

太赫兹波探测技术在天文、国防、安检以及生物等领域发挥着越来越重要的作用.随着技术的发展,太赫兹探测器的灵敏度在不断提高,目前已经发展到单光子探测水平.在太赫兹频段,由于光子能量低,传输损耗较大,太赫兹单光子探测器的研制开发面临极大的技术挑战.本文首先介绍了太赫兹单光子探测器的基本原理、主要指标和测试系统并提出了实现太赫兹单光子探测的基本要求.然后,介绍了几种常见的太赫兹单光子探测器,包括半导体量子点探测器、量子阱探测器以及超导量子电容探测器,并对这些器件的发展历史、工作原理和性能指标进行了概述.半导体量子点探测器以及量子阱探测器可以实现10-21W/Hz1/2量级的噪声等效功率,并且具有很大的电流响应以及动态范围,但是其量子效率较低.超导量子电容探测器目前已实现1.5 THz的单光子探测,其噪声等效功率优于10~(-20)W/Hz~(1/2)并且探测效率可达90%.此外,纳米测热辐射计等太赫兹探测器也展现了太赫兹单光子探测的前景,本文对其工作原理和发展现状进行了介绍.结合目前国际上的重大研究项目以及报道的应用实例分析了太赫兹单光子探测器在太赫兹成像、天文观测、量子信息等领域的应用前景,阐述了太赫兹单光子探测器在这些应用中的优势.最后,对太赫兹单光子探测器的性能指标进行了总结并对未来的发展趋势进行了展望.     

铜(Ⅱ)-杂环碱-赖氨酸配合物的稳定性研究

用pH电位滴定法研究了在乙醇-水介质(φ(乙醇)=30%;I(NaClO4)=0.1 mol/L,t=(25±1) ℃)中Cu(Ⅱ)与杂环碱(2,2′-联吡啶(Bpy)或邻菲咯啉(Phen),配体A)和赖氨酸(Lys,配体B)形成配合物的行为;测定了Cu(Ⅱ)-Lys二元配合物和Cu(Ⅱ)-杂环碱-Lys三元配合物的稳定常数.三元配合物相对于二元配合物的稳定性用ΔlgKM(ΔlgKM=lgKMAMAB-lgKMMB)表示.结果表明,二元配合物的稳定常数较大且ΔlgKM值均大于理论统计值.这可能与Lys分子侧基的推电子效应及三元配合物中存在的πA←M←πB电子效应等因素有关.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with