Broadband mid-infrared pulse via intra-pulse difference frequency generation based on supercontinuum from multiple thin plates

We report on the generation of optical pulses with a nearly one octave-spanning spectrum ranging from 1300 nm to2500 nm at 1 kHz repetition rate, which are based on intra-pulse difference frequency generation(DFG) in β-barium borate crystal(β-BBO) and passively carrier-envelope-phase(CEP) stabilized. The DFG is induced by few-cycle pulses initiated from spectral broadening in multiple thin plates driven by a Ti: sapphire chirped-pulse amplifier. Furthermore, a numerical simulation is developed to estimate the conversion efficiency and output spectrum of the DFG. Our results show that the pulses from the DFG have the potential for seeding intense mid-infrared(MIR) laser generation and amplification to study strong-field physics and attosecond science.

Theoretical research on terahertz wave generation from planar waveguide by optimized cascaded difference frequency generation

A novel scheme for high-efficiency terahertz(THz)wave generation based on optimized cascaded difference frequency generation(OCDFG)with planar waveguide is presented.The phase mismatches of each-order cascaded difference frequency generation(CDFG)are modulated by changing the thickness of the waveguide,resulting in a decrement of phase mismatches in cascaded Stokes processes and an increment of phase mismatches in cascaded anti-Stokes processes simultaneously.The modulated phase mismatches enhance the cascaded Stokes processes and suppress the cascaded anti-Stokes processes simultaneously,yielding energy conversion efficiencies over 25%from optical wave to THz wave at 100 K.

High-efficiency terahertz wave generation with multiple frequencies by optimized cascaded difference frequency generation

High-efficiency terahertz(THz) wave generation with multiple frequencies by optimized cascaded difference frequency generation(OCDFG) is investigated at 100 K using a nonlinear crystal consisting of a periodically poled lithium niobate(PPLN) part and an aperiodically poled lithium niobate(APPLN) part.Two infrared pump waves with a frequency difference ω_(T1) generate THz waves and a series of cascaded optical waves in the PPLN part by cascaded difference frequency generation(CDFG).The generated cascaded optical waves with frequency interval ω_(T1) then further interact in the APPLN part by OCDFG,yielding the following two advantages.First,OCDFG in the APPLN part is efficiently stimulated by inputting multi-order cascaded optical waves rather than the only two intense infrared pump waves,yielding unprecedented energy conversion efficiencies in excess of 37% at 1 THz at 100 K.Second,THz waves with M timesω_(T1) are generated by mixing the mth-order and the(m+M)th-order cascaded optical waves by designing poling period distributions of the APPLN part.

Energy Scaling of Terahertz Pulses Produced through Difference Frequency Generation

We study the energy scaling of terahertz (THz) emission through difference frequency generation of near-infrared pulses, and demonstrate that Gigawatt few-cycle THz transients at the central frequency of 30 THz are produced from GaSe crystal pumped by two pulses at 1.65 and 1.95 micrometers, with the high quantum yield of 28%. Our analysis indicates that the high yield of DFG originates from the largely reduced group velocity mismatch as the long-wavelength pumping pulses are employed.

Creation of multi-frequency terahertz waves by optimized cascaded difference frequency generation

A new scheme which generates multi-frequency terahertz(THz)waves from planar waveguide by the optimized cascaded difference frequency generation(OCDFG)is proposed.A THz wave with frequencyω_(T1)is generated by the OCDFG with two infrared pump waves,and simultaneously a series of cascaded optical waves with a frequency intervalω_(T1)is generated.The THz wave with a frequency of M-timesω_(T1)is generated by mixing the m-th-order and the(m+M)-th-order cascaded optical wave.The phase mismatch distributions of cascaded difference frequency generation(CDFG)are modulated by changing the thickness of planar waveguide step by step,thereby satisfying the phase-matching condition from first-order to high-order cascaded Stokes process step by step.As a result,the intensity of THz wave can be enhanced and modulated by controlling the cascading order of OCDFG.

In vitro and in vivo cell tracking of chondrocytes of different origin by fluorescent PKH 26 and CMFDA

Tissue engineering techniques for cartilage re-pair to heal defects in joint surfaces is a clinical practice. Harvested autologous chondrocytes are expanded in culture and delivered in a suitable carrier medium back into the patient>s joint de-fect. The defect is then subsequently filled by new cartilage. Whether the cells in the repair tissue originate from the engineered tissue of the host or are derived from the surrounding original cartilage remains a relevant question for the ap-plied therapy. To answer this several methods exist to track cells, such as transfection of cells with LacZ carrying viruses, radio labeling with 111 IN or 51 Cr or fluorescent labeling with FDA. However, these techniques have drawbacks such as they may influence cellular properties, are radioactive and or quickly lose their tracking ability. New fluorescent probes are easier to handle and do not to interfere with cells. PKH 26劌 is a relatively new cell-labeling agent, but few data exist on the application of this dye in chondrocytes in vitro and in vivo. 5-chloromethylfluorescein diacetate - CMFDA (¨cell tracker green〔) is an established fluores-cent probe for imaging the dynamic processes of cell proliferation in vitro and in vivo. Likewise, several studies exist on different cell types. However, little data are available for chondro-cytes. The first aim of the study was to evaluate qualitative differences in fluorescence pattern after labeling of articular, auricular and costal chondrocytes. Secondly, we evaluated the influ-ence of labeling with CMFDA on cellular adhe-sion properties. The third aim was to compare the duration of cell labeling of chondrocytes of different origin with established CMFDA as stan-dard and PKH 26潴 for 3 cell generations in vitro and 12 weeks in vivo. We show that chondro-cytes from different origin can be labeled effec-tively with both PKH 26潴 and CMFDA. The PKH 26潴 labeled articular chondrocytes maintained fluorescence longer than CMFDA in vitro and in vivo. A higher percentage of articular chondro-cytes remained stained at 63 days than auricular or costal chondrocytes.

Mid-IR dual-wavelength difference frequency generation in uniform grating PPLN using index dispersion control

A novel widely tunable dual-wavelength mid-IR difference frequency generation （DFG） scheme with uniform grating periodically poled lithium niobate （PPLN） is presented in this paper. By using the temperature-dependent dispersion property of PPLN, the quasi-phase matching （QPM） peak for the pump may evolve into two separate ones and the wavelength spacing between them increases with the decrease of the crystal temperature. Such two pump QPM peaks may allow simultaneous dual-wavelength mid-IR laser radiations while properly setting the two fundamental pump wavelengths. With this scheme, mid-IR dual-wavelength laser radiations at around 3.228 and 3.548, 3.114 and 3.661, and 3.019 and 3.76 μm, are experimentally achieved for the crystal temperatures of 90, 65, and 30 ℃, respectively, based on the fiber laser fundamental lights.

Generation of Higher Terahertz Harmonics in Nonlinear Paraelectrics under Focusing in a Wide Temperature Range

It is theoretically investigated the generation of higher harmonics of two-dimensional and three-dimensional terahertz electromagnetic beams in nonlinear crystals. The attention is paid to crystalline paraelectrics like SrTiO3 under the temperatures 60 - 200 K, these crystals possess the cubic nonlinearity. The bias electric field is applied to provide the dominating quadratic nonlinearity. The initial focusing of the beams not only increases the efficiency of generation of higher harmonics, but alto makes possible to select maxima of different higher harmonics at some distances from the input. At lower temperatures the nonlinearity behaves at smaller input amplitudes, whereas at higher temperatures the harmonic generation can be observed at higher frequencies up to 1.5 THz. In three-dimensional beams the peak amplitudes of higher harmonics can be bigger than in two-dimensional beams, but the ratios of these peak values to the maximum values of the focused first harmonic are smaller than in two-dimensional beams.

Computational Analysis of the Effect of Nano Particle Material Motion on Mixed Convection Flow in the Presence of Heat Generation and Absorption

The present study is concerned with the physical behavior of the combined effect of nano particle material motion and heat generation/absorption due to the effect of different parameters involved in prescribed flow model.The formulation of the flow model is based on basic universal equations of conservation of momentum,energy and mass.The prescribed flow model is converted to non-dimensional form by using suitable scaling.The obtained transformed equations are solved numerically by using finite difference scheme.For the analysis of above said behavior the computed numerical data for fluid velocity,temperature profile,and mass concentration for several constraints that is mixed convection parameterλt,modified mixed convection parameterλc,Prandtl number Pr,heat generation/absorption parameterδ,Schmidt number Sc,thermophoresis parameter Nt,and thermophoretic coefficient k are sketched in graphical form.Numerical results for skin friction,heat transfer rate and the mass transfer rate are tabulated for various emerging physical parameters.It is reported that in enhancement in heat,generation boosts up the fluid temperature at some positions of the surface of the sphere.As heat absorption parameter is decreased temperature field increases at position X=π/4 on the other hand,no alteration at other considered circumferential positions is noticed.

THz wave generation by repeated and continuous frequency conversions from pump wave to high-order Stokes waves

We propose a novel scheme for THz wave generation by repeated and continuous frequency conversions from pump wave to high-order Stokes waves(HSWs).The repeated frequency conversions are accomplished by oscillations of Stoke waves in resonant cavity(RC)where low-order Stokes waves(LSWs)are converted to high-order Stokes waves again and again.The continuous frequency conversions are accomplished by optimized cascaded difference frequency generation(OCDFG)where the poling periods of the optical crystal are aperiodic leading to the frequency conversions from low-order Stokes waves to high-order Stokes waves uninterruptedly and unidirectionally.Combined with the repeated and continuous frequency conversions,the optical-to-THz energy conversion efficiency(OTECE)exceeds 26%at 300 K and 43%at 100 K with pump intensities of 300 MW/cm^(2).

Noise-like pulse generation from a thulium-doped fiber laser using nonlinear polarization rotation with different net anomalous dispersion

A mode-locked thulium-doped fiber laser(TDFL) based on nonlinear polarization rotation(NPR) with different net anomalous dispersion is demonstrated. When the cavity dispersion is-1.425 ps^2, the noise-like(NL) pulse with coherence spike width of 406 fs and pulse energy of 12.342 nJ is generated at a center wavelength of 2003.2 nm with 3 dB spectral bandwidth of 23.20 nm. In the experimental period of 400 min, the 3 dB spectral bandwidth variation, the output power fluctuation, and the central wavelength shift are less than 0.06 nm, 0.04 d B, and0.4 nm, respectively, indicating that the NPR-based TDFL operating in the NL regime holds good long-term stability.

当代陶瓷艺术与综合材料的融合研究

陶瓷艺术多样化历来是不同时代共同关注的问题,同样对陶瓷艺术的创新方式与呈现形式也在不断地突破革新。笔者从传统陶瓷艺术形式的概念入手,分析比较陶瓷材料与综合材料的边界与差异、探讨艺术形式的更多可能性,探究分析当代陶瓷艺术与综合材料融合创作的时代语言与形式语言。

论中国哲学典籍翻译

该文着眼于中国哲学典籍翻译研究,从现状中发现问题,从问题中拓寻创新之路径,于创新路径中深切体会中西哲学的本质差异,了解中国本土哲学的真谛,从中得出翻译好中国哲学典籍作品的关键在于以中西哲学之眼观中国哲学典籍之独有特色,将中西哲学差异的整体思维观,置于翻译的全过程之中。翻译中国哲学典籍是世界了解中华文明思想精髓的重要传播途径,是建立中国哲学话语与概念系统的手段,更是树立、培养文化自信的关键步骤。作为新时代译者,需在深入了解本国文化根基、吸收外来学说的同时,不忘本民族之地位;深入了解中西方哲学及其差异,将具有鲜明中国特色的文化传播至世界。

基于专业差异化《纲要》课实践教学模式构建

思想政治教育立足专业差异推行个性化实践教学,有利于增强教学针对性、推进实践教学创新、促进学生全面成长。但受各种因素影响,目前高校《中国近现代史纲要》(以下简称《纲要》)课实践教学存在实践教学目标统一化、教学内容同质化、教学方法形式化、教学考核笼统化等问题,严重影响了实践教育目的实现。要优化《纲要》课实践教学,需在遵守实践教学总目标前提下,应用差异化教学理念,以学生知识取向不同制定差异化实践教学目标,以学生专业兴趣不同设计差异化教学内容,以学生思维方式不同采取差异化教学方法,以实践教学类别不同实行差异化考核,形成“四位一体”差异化实践教学模式,增强实践育人功能。

我国人才分布现状及主要影响因素

根据我国现行人才标准,以2010年全国第六次人口普查和2011年全国统计年鉴为依据,以省级行政区域为单位,统计2010年本科及以上学历人口的密度分布,发现当代全国人才分布极不均衡,东部地区高于西部地区,京、沪、津、苏、浙、陕、卾、黑、吉、辽等人才密度高.国家政策、经济社会发展水平、高等院校布局及自然环境等因素共同作用,促使高学历人口向大中城市、发达地区集聚.

杜威哲学的现代意义

评价杜威实用主义的现代意义,需要在马克思在哲学上的革命变更和西方哲学由近代到现代的转型的大背景下考察杜威哲学的根本意义及其与西方哲学发展趋势及马克思主义哲学的关系。本文认为杜威哲学的根本意义是对现实生活和实践的强调;杜威的哲学改造适应了西方哲学现代变革的潮流;杜威哲学与马克思的哲学有着原则区别,但在超越近代哲学的局限性、体现现代哲学的发展趋势上二者殊途同归。。

危机时刻的文学批评——以钱锺书、奥尔巴赫、巴赫金为对照的阐释

钱锺书抗战时期撰写的《谈艺录》,与奥尔巴赫的《摹仿论:西方文学中现实的再现》和巴赫金的《拉伯雷和他的世界》都是在民族的危机时刻写就的,三者可以被视为世界比较文学事件作对照性阅读。这三本书无论就体例、风格、方法学以及世界观而言都极为不同。但它们既成于战时,作者面对文明崩解以及个体生命的困顿,都有不能已于言者的反思,而他们所展现的宏大历史视野、浑厚的学术知识、锐利的批评洞见,俨然为“发愤著书”平添现代意涵。有关这三位学者及其论述的阐释所在多有,但最值得注意的,与其说是个别著作的深入解析,不如说是面对“危机时刻”,钱锺书、奥尔巴赫、巴赫金为何及如何从文学入手,寻求因应之道,他们在批评文字里所投注的情感以及赖以发挥的意象。由此可以考察除了历史因缘外,三部经典为我们带来的方法学启示和与此时此地的文化政治的关联。

当代研究生价值观现状及其在人口学变量上的差异分析

为了解当代硕士研究生的价值观取向,采用中国人价值观问卷(Chinese Value Questionnaire,CVQ)调查河南省6个城市8所高校的1112名硕士研究生。结果发现,当代研究生价值观八个维度上的得分在3.37~4.78之间,认同度由强到弱依次为才能务实、品格自律、人伦情感、公共利益、守法从众、家庭本位、金钱权力、名望成就;当代研究生价值观在性别、家庭所在地、硕士类型、所读院校、读研之前的学历、家庭结构等人口学变量上差异显著,在是否为独生子女、年级上差异不显著。

试论当代仿古玉与传统仿古玉的区别

仿古玉是中国古代玉器发展到一定阶段的特殊产物,历史上以宋代、清代为代表。当代仿古玉在现代科技水平和时代风格的影响下,既继承传统,相比传统又存在着较大区别。文章以材料使用、工艺特点以及艺术风格为主要研究对象,对传统与当代仿古玉的区别进行了论述与总结,并对当代仿古玉的发展方向提出思考和建议。

《现代汉语词典》与《现代汉语规范词典》异形词收录探析

《现代汉语词典》与《现代汉语规范词典》都按有无国家试行标准两大类分别收录处理异形词,但它们在分条立目、对同组异形词推荐词形与非推荐词形的界定、对异形词推荐词形与非推荐词形词语间语义关系的认定及对非推荐词形异形词的标注形式等方面都有差异。差异主要成因在于两者对异形词收录原则有不同理解。相对而言,《现代汉语词典》更强调"从简"、"系统性",《现代汉语规范词典》更强调"理据性"、"规范性"。《现代汉语词典》和《现代汉语规范词典》对异形词所做的整理性收录,正在并仍将对现代汉语异形词表的审定产生积极影响,有助于现代汉语词汇规范化。