新型电光调Q腔内倍频绿光激光器

本文报道了一种新型的LD泵浦Nd:YVO4-KTP电光调Q绿光激光器,用单块KTP晶体同时作为电光调Q开关和Ⅱ类相位匹配的倍频晶体,减少了腔内损耗,提高了效率,得到了脉宽为12ns的绿光脉冲序列。激光器采用纵向同轴泵浦方式、独特的整体控温技术和小焦距非球面聚焦透镜,并把全部元件固化为一个整体,进一步提高了器件的效率、激光的输出功率和光束方向的稳定性。     

高亮度固体激光器技术发展研究

激光推进、激光传能等重大科研方向对高亮度固体激光器技术提出了重大需求,使得相关研究持续成为国际关注焦点。本文阐述了高亮度固体激光器技术的宏观需求,梳理国内外的技术研究现状并总结发展趋势,凝练技术进一步发展所面临的问题;据此完成高亮度固体激光器的关键技术分析,并结合国情提出未来发展建议。板条激光器和光纤激光器由于具有突出优点成为研究热点,在单台激光器输出功率不断提升的同时,可配合光束合成方法来实现高亮度激光输出。研究表明,应着重推动新型激光材料、高端半导体激光泵浦源、高精度封装工艺、自适应光束控制、光束合成关键器件等方面的技术攻关,尽快形成核心技术体系;科学布局以表层增益板条激光器技术为代表的、具有良好发展潜力的固体激光器技术研究课题,加强共用基础技术研究与积淀,为未来固体激光器输出亮度、转换效率、功率质量比的持续提升奠定坚实基础。     

连续Nd:YAG激光器输出功率稳定性研究

本文介绍一种用两套LiNbO3晶体作电光调制器,高稳定硅光电二极管作光反馈控制信号的激光稳功率仪串联使用来稳定Nd:YAG激光器输出功率的方法。对于输出功率为5瓦左右,本身输出功率稳定度为10%/小时的Nd:YAG激光器,其输出光束经稳功率系统后,其稳定度为0.2/小时。     

He-Ne激光器输出功率的稳定及稳定性的测试方法

一、前言He-Ne 激光器是应用较广泛的激光器。但在不加稳定措施时,这类激光器的输出功率长期稳定性很难达到2%。为此我们开展了He-Ne 激光器输出功率的稳定工作。在一九七六年,我们用本文谈及的装置可将 He-Ne 激光功率稳定在±0.1～±0.15%(测量时间为半小时)。经过几年运转的实践证明,其工作是可靠的。本装置要求不稳定光束的功率波动不大于10%。二、原理He-Ne 激光器输出功率的稳定装置是利     

高重复频率LD侧面泵浦Nd∶YAG电光调Q激光器

文中介绍二极管激光侧泵浦 Q开关激光器 ,激光介质是 Nd∶YAG板条 ,几何尺寸为 2 0 .3mm× 5 mm× 2 .5 mm,二极管激光与板条之间用柱透镜耦合 ,激光谐振腔为平凹腔 ,输出镜曲率半径为 1m,透光率 T=0 .33。用 KD★ P电光 Q开关 ,得到输出脉宽为 12 .7ns、单脉冲能量 1.97m J的激光 ,光束质量 M2x=2 .6 9、M2y=1.87,重复频率 98Hz     

项目与资本

光电功能晶体 本项目主要是通过熔盐、提拉生长技术生产LBO、BBO晶体、YVO4、Nd:YVO4等晶体并经光学加工,镀膜制成供激光器用的变频元件,光纤通讯用的光隔离器元件及激光器件。 利用激光通过非线性光学晶体对激光波长进行变频制成光参量振荡器,可获得从紫外到红外波长输出的激光光源。其可调谐范围、转换效率、输出功率以及可靠性等方面均优于染料激光器。在激光器中使用LBO、BBO等非线性光学晶体实现了光参量激光器和可见/紫外大功率全固态激光器商品化,推动了激光显示、光信息存储、微电子机械加工、医疗、核能源以及在军事上的应用。 LBO、BBO非线性光学晶体拓宽了激光器的应用领域,由于推广迅速,市场呈快速增长趋势,在短短的几年内形成了一千多万美元的市场规模。随着全固态激光器逐步取代现用的离子激光器,大屏     

多模式工作激光器的研究

目的:研究一台激光器多种模式工作的特性以及不同模式之间的转换。方法:设计一台双腔钛宝石激光器,采用双光束泵浦方式,通过锁模和光学元件的替换实现激光器的多模式工作。结果:连续运转状态下,两个激光腔的输出为可调谐连续输出;两个激光腔都进行色散补偿时,锁模激光器输出两列飞秒光脉冲;锁模状态下,只有一个激光腔进行色散补偿时,该激光腔输出飞秒光脉冲,而另外一个激光腔没有进行色散补偿,输出皮秒光脉冲。结论:多种模式工作的激光器适用于多种领域的研究与应用。     

靶蒸气等离子体对高功率激光的反射效应

置于真空靶室中的金属靶 ( Fe) ,在高功率激光作用下产生的高密度等离子体 ,对入射激光有较强的受激布里渊散射效应。这种逆着入射激光方向的散射光 ,在5× 1 0 1 1 W/cm2 的激光功率密度作用下 ,后向散射能量是 0 .1 6 J。这种后向散射光 (反射 ) ,在激光器系统不加光学隔离的情况下 ,又反馈回来 ,使激光器某单元形成激光振荡 ,在激光器高功率单脉冲输出之后 ,又产生很强的自由振荡激光输出 ,使激光力学效应物理实验出现导常现象     

60瓦半导体激光器光纤耦合器件

应用光纤列阵耦合方式，对大功率半导体激光器线列阵输出光束的快轴方向用一根柱透镜准直，准直后的光束耦合到光纤列阵中，实现出纤功率为60瓦的大功率半导体激光二极管线列阵光纤耦合器件，耦合效率大于80％，光纤的数值孔径NA为0．11。     

2 kW半导体激光焊接铝合金工艺研究

为实现半导体激光器对铝合金的焊接,将2 kW半导体激光器的光束进行整形,提高光束质量,光束亮度达到412.00 MW/cm~2.sterad,比整形前的光束亮度增加了7倍。然后采用整形的半导体激光器对1 mm厚度的6063铝合金进行拼接焊接实验,通过对焊接工艺参数激光功率、焊接速度、离焦量进行正交优化实验,焊缝接头最大抗拉强度为172.3 MPa,达到母材的85%,实现了半导体激光对铝合金的激光焊接目标。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.