一种激光折叠腔稳定性分析及设计的新方法

为了对激光谐振腔进行优化设计,运用光学传输矩阵理论,借助V型折叠腔激光器的等效简化模型对该激光腔的稳定性进行了研究.分析了腔长、折叠镜焦距、反射镜曲率半径与系统稳定性的关系,得到以失调量为参数的稳区临界曲线方程,实现了三镜折叠腔型CO2斩光盘式调Q脉冲输出激光器的设计.分析结果表明,对于子腔预先给定的参量,只要另一子腔满足适当的失调量,整个谐振腔就是稳定的.任一子腔内有二个稳定区而非以往研究者提出的一个稳定区,可根据需要选取最佳的稳定点.采用失调量而非g因子作为参数,直接给出稳定区范围和失调误差,使用性好.     

基于V型谐振腔的热稳定性分析

为了提高V型谐振腔的热稳定性,采用了图解分析法,将V型折叠腔等效为腔内含有一个透镜的共轴球面腔。同时考虑到晶体热透镜效应,结合多元件光学谐振腔的等价腔分析法,将等效后腔内含透镜组的多元件球面腔近似等价为腔内不含透镜的共轴球面空腔。对V型腔等价后的共轴球面空腔的稳定性进行了理论计算和仿真分析。结果表明,当总腔长为75mm、折叠角为0.15π左右时,谐振腔具有最宽的热稳定范围;此时若增益介质与折叠镜的间距为28mm,则谐振腔能适应的最小热透镜焦距可达12mm。这一结果体现了谐振腔关键参量对热稳定性的重要影响,对激光腔型稳定性的优化设计具有一定的指导意义。     

直角内圆锥面全反镜折叠腔激光器的输出特性

为简化高功率激光器谐振腔结构,提高激光谐振腔的稳定性特别是热稳定性,增加基模体积,改善光束质量,采用直角内圆锥面反射镜作为全反镜,平行平面镜作为输出镜组成新型激光谐振腔.实验结果表明,在圆锥全反镜失调角小于37.3′时,圆锥折叠腔激光器的单脉冲输出能量下降小于5%,且近场输出光斑没有明显变化;经模式仪分析表明,圆锥折叠腔激光近场光强分布均匀.圆锥反射镜折叠具有非常强的抗失调能力,结构简单,便于安装调整,特别适合于恶劣环境下的强激光系统应用.     

激光V型腔参量对输出性能的影响

在激光腔型设计时，为了使激光具有良好的输出性能，需要找出谐振腔参量对激光输出性能的影响规律。结合V型折叠腔的图解分析法和多元件光学谐振腔的等价腔分析法，将折叠腔近似等价后，对等价的共轴球面空腔的稳定性和输出光束质量进行理论求解分析，找到了V型折叠腔参量和激光输出性能的内在联系。通过计算给定的条件可知，当折叠角=0.15时，总腔长L的理想取值范围为（70，80）mm，最佳取值为75 mm，端面镜曲率半径R1、R2的允许变化范围为（60，75）mm，折叠镜曲率半径R3的最小取值为45 mm，随着左（右）侧子腔g-参数积增大，右（左）侧端面镜上的基模光斑半径和远场发散角增大。上述等价腔分析法和结论对激光腔型优化设计提供了重要的理论依据。     

折叠腔失调灵敏度随腔参数的变化

本文讨论了所有元件都失调的折叠腔的失调灵敏度,并用数值计算研究了失调灵敏度随谐振腔参数的变化。     

LD双端端面抽运Nd：YVO_4折叠腔主振荡器的稳定性研究

对双端端面抽运的Nd:YVO4Z型折叠腔主振荡器的设计进行了模拟,采用ABCD传输矩阵理论详细分析了各腔参量对谐振腔稳定性的影响.由模拟结果推断,稳区的范围可通过谐振腔各分臂臂长的和来调节,而且应在臂长允许的范围内尽量选择小角度.利用相同的光学元件设计了两种腔长的热稳定腔,比较了长短腔型各自的利弊.     

改性KTP晶体、三镜折叠腔内倍频研究

本文利用改性ＫＴＰ晶体,进行了纯连续激光倍频实验。根据光束传输矩阵,用计算机数值法计算了三镜折叠腔不同谐振腔参数所对应的稳定区,对Ｎｄ：ＹＡＧ／ＫＴＰ进行腔内倍频,实验获得了３－５Ｗ 纯连续绿色激光输出。其实验结果与理论计算值基本相符。     

多元件光学谐振腔的失调灵敏度

本文证明,通过引入等价g~*-参数和等价腔长L~*,多元件谐振腔的失调灵敏度参量可以由空腔的失调灵敏度参量D得出.对各种腔型的脉冲YAG激光器作了实验研究并证实了理论.     

约束稳定和不稳定的非共振环形腔

本文使用传播矩阵(G参数等价腔)方法详细研究了约束稳定和不稳的非共振环形腔的光束特性。分别推导出满足约束稳定条件、热稳条件的调整量δ和失调量△的公式。对不稳非共振环形腔的本征球面波作了分析,推导出满足广义共焦条件的调整量δ的公式。数值计算不仅证实了我们的理论分析,并且说明了如何选取腔参数来达到设计要求。     

LD双端端面抽运Nd∶YVO4折叠腔主振荡器的稳定性研究

对双端端面抽运的Nd∶YVO4Z型折叠 腔主振荡器的设计进行了模拟,采用ABCD传输矩阵理论详细分析了各腔参量对谐振腔稳定性的影响。 由模拟结果推断,稳区的范围可通过谐振腔各分臂臂长的和来调节,而且应在臂长允许的范围内尽量选 择小角度。利用相同的光学元件设计了两种腔长的热稳定腔,比较了长短腔型各自的利弊。     

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.     

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.     

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.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

中国建立EB级存储实验室,致力云计算应用(英文)

正With the support of 863 programs,Sugon Information Industry Co.,Ltd.,set up a dawning EB-class storage laboratory to address massive data storage requirements and largescale cloud computing demonstration applications.The Dawning EB-class cloud storage system adopts advanced fault-tolerant architecture,efficient data fault-tolerant algorithms with user authentication and data encryption policies to deal with the"lost""wrong"and"stolen"problems of data for ensuring the reliability and safety of the EB-class storage system in the public network application environments.The Dawning EB-class Storage Laboratory taking advan-