879 nm直接抽运提高Nd:GdVO4激光器性能

激光二极管(LD)大功率端面抽运固体激光器(DPSSL)中的热效应会影响到激光器的各个方面,使得激光输出效率下降,光束质量变坏、谐振腔的稳定性变差等.采用新波段879 nm取代808 nm,将粒子直接激励到激光发射上能级,降低无辐射弛豫过程产生的热量,有效地减少热的产生,降低激光二极管端面抽运Nd:GdVO4晶体的热效应,获得更高性能的激光输出.在相同条件下通过879 nm激光二极管直接端面抽运及808 nm激光二极管间接端面抽运Nd:GdVO4激光器的实验比较,结果表明,在较高抽运功率下采用879 nm抽运提高了Nd:GdVO4激光器的激光输出性能.最后采用879 nm激光二极管端面抽运Nd:GdVO4晶体棒直线腔方案,在16.3 W的吸收抽运功率下,获得最大连续输出功率9.8 W的TEM00模1063 nm激光输出,对吸收抽运光的光-光转换效率高达60.1%,斜率效率达68.4%.     

879nm直接抽运提高Nd∶GdVO_4激光器性能

激光二极管(LD)大功率端面抽运固体激光器(DPSSL)中的热效应会影响到激光器的各个方面,使得激光输出效率下降,光束质量变坏、谐振腔的稳定性变差等。采用新波段879 nm取代808 nm,将粒子直接激励到激光发射上能级,降低无辐射弛豫过程产生的热量,有效地减少热的产生,降低激光二极管端面抽运Nd∶GdVO4晶体的热效应,获得更高性能的激光输出。在相同条件下通过879 nm激光二极管直接端面抽运及808 nm激光二极管间接端面抽运Nd∶GdVO4激光器的实验比较,结果表明,在较高抽运功率下采用879 nm抽运提高了Nd∶GdVO4激光器的激光输出性能。最后采用879 nm激光二极管端面抽运Nd∶GdVO4晶体棒直线腔方案,在16.3 W的吸收抽运功率下,获得最大连续输出功率9.8 W的TEM00模1063 nm激光输出,对吸收抽运光的光-光转换效率高达60.1%,斜率效率达68.4%。     

晶体热效应对激光二极管抽运调Q固体激光器转换效率的影响

研究了在考虑晶体热效应的情况下,如何最优化设计激光二极管(LD)端面抽运的固体激光器。综合考虑抽运光束分布、抽运功率、谐振腔结构以及激光介质的热效应对激光器转换效率的影响,给出设计激光器的一套仿真计算算法。结果表明,热致衍射损耗与抽运光半径、抽运功率、腔长、振荡光半径以及晶体材料有关,与输出镜透射率以及重复频率无关。在考虑热致衍射损耗的情况下,当抽运功率一定时,最佳的抽运光参数和谐振腔参数能使Nd:YAG的转换效率最大。     

LD连续和脉冲抽运的Nd：YAG腔内倍频蓝光激光器

在激光二极管连续抽运的Nd：YAG激光器中,分别采用BIBO和LBO晶体对946nm激光进行腔内倍频,获得473 nm蓝光输出。抽运功率9.5 W时,BIBO晶体倍频输出功率为508mW,转换效率5.35%：LBO晶体倍频输出功率为441 mW,转换效率4.64%。LBO倍频的转换效率小于BIBO,但输出蓝光的光束空间质量较好。在LD脉冲抽运和LBO晶体腔内倍频的Nd：YAG激光器中,研究了抽运脉冲的调制频率和占空比与蓝光输出功率的关系。当抽运功率9W,脉冲调制频率100Hz、占空比60%时,得到最大的蓝光输出功率465mW,比相同功率连续抽运提高87mW。结果表明,LD脉冲抽运能有效降低Nd：YAG晶体的热效应影响,提高激光器输出功率。     

LD端面抽运1.5μm Er3+,Yb3+∶YAl3（BO3）4激光器

报道了一种基于Er3+,Yb3+∶YAl3(BO3)4晶体的1.5μm固体激光器。为了解决由晶体严重的热效应所导致的激光器转化效率较低以及无法连续运转的问题,对控温炉设计以及抽运光源参数,如调制频率、占空比和腰斑尺寸等,进行了实验优化,从而减小了晶体的热负载,提高了准连续激光器的输出性能。在抽运源调制频率为40Hz,占空比为10%,抽运光腰斑半径为80μm,注入功率为17.6W时,获得了2.6W的准连续1.5μm激光输出,斜率效率为18.1%;同时在抽运功率为5W时,实现了290mW的连续单横模1.5μm激光输出,斜率效率为8.5%。     

连续波500 W全固态Nd:YAG激光器研究

研制了全国产化全固态半导体激光器(LD)抽运模块，Nd：YAG激光输出功率达500W。介绍了优化抽运模块结构参数的程度。从增益分布特性等方面，介绍了研究其输入-输出功率特性的实验装置，随着抽运功率的增加，Nd：YAG激光输出以斜率效率47％线性增加，最大输出功率达到575W，光-光转换效率达26．1％。采用He-Ne激光探测法实验测量了该抽运模块中的热透镜效应。通过测量热焦距，分析了其热透镜效应：热透镜焦距与抽运功率成反比，抽运功率很小时，热焦距大，热透镜效应很小，被Nd；YAG棒的修凹面补偿，所以此时热焦距较大，热效应不显著。随着抽运功率的增大，热焦距减小，热透镜效应越来越显著。     

角抽运Nd∶YAG复合板条1.1μm多波长连续运转激光器

报道了一种适合中小功率输出的全固态激光器的角抽运方法,抽运光从板条激光器中板条晶体的角部入射,可获得较高的抽运效率和较好的抽运均匀性。采用单角抽运方式,进行了角抽运Nd∶YAG复合板条1.1μm多波长连续运转激光器的实验研究。激光腔采用紧凑型平平直腔结构,腔长仅为22 mm。当注入抽运功率为50.3 W时,1.1μm多波长激光连续输出功率最高达10.9 W,光光转换效率为21.7%,斜率效率为22%。当注入抽运功率为48 W时,1.1μm多波长激光连续输出功率短期不稳定性小于0.6%。     

LD抽运Nd:KGW薄片激光器的研究

为了解决Nd：KGW的热效应问题，提出了端面冷却方法，并研究了LD面抽运Nd：KGW薄片激光器的性能。针对LD端面抽运Nd：KGW激光器，计算了激光介质表面的温度分布。计算结果表明，Nd：KGW晶体的热效应相当严重。该激光器外推抽运阈值为300mW。虽然谐振腔损耗高达4．06％，激光器的最大斜效率仍达到30．49％。输入功率为3．2w时晶体被打裂，比类似文献中报道的数值高出大约1W。     

高功率激光二极管端面抽运复合晶体激光器的研究

在高功率激光二极管抽运固体激光器中,热效应已成为获得高输出功率和高光束质量的最大阻碍因素.用有限元方法研究了高功率激光二极管端面抽运Nd∶YVO4激光器中热透镜分布规律,提出了用复合晶体消除热透镜效应的方法.研究表明在端面抽运的传统单一Nd∶YVO4晶体激光器中,由于抽运功率密度很高,热透镜效应非常严重,由端面变形而造成的热透镜效应约占整个热透镜效应的50%;而采用复合晶体能够很好地消除由端面变形而造成的热透镜效应,同时得到很好的冷却效果,获得比采用传统单一晶体高出许多的基模输出功率和更好的光束质量.实验证明,采用复合结构晶体在23 W的抽运功率水平下得到了11 W的基模输出功率,光束质量因子M2 <1 5,光光转换效率达到48%.     

连续波500W全固态Nd∶YAG激光器研究

研制了全国产化全固态半导体激光器(LD)抽运模块,Nd∶YAG激光输出功率达500W。介绍了优化抽运模 块结构参数的程度。从增益分布特性等方面,介绍了研究其输入 输出功率特性的实验装置,随着抽运功率的增加, Nd∶YAG激光输出以斜率效率47%线性增加,最大输出功率达到575W,光 光转换效率达26.1%。采用He Ne 激光探测法实验测量了该抽运模块中的热透镜效应。通过测量热焦距,分析了其热透镜效应:热透镜焦距与抽运 功率成反比,抽运功率很小时,热焦距大,热透镜效应很小,被Nd∶YAG棒的修凹面补偿,所以此时热焦距较大,热 效应不显著。随着抽运功率的增大,热焦距减小,热透镜效应越来越显著。     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.