LDA端泵电光调QNd：YAG激光器

用峰值功率600W的准连续（QCW）激光二极管阵列（LDA）端泵浦Nd:YAG晶体，耦合装置为微柱透镜阵列和透镜导管，KD^*P晶体作为Q开关。在单脉冲泵浦能量93mJ条件下，得到了脉宽10ns，能量10mJ的短脉冲输出，光-光转换效率11%。实验给出了调Q输出脉冲宽度与能量随泵浦参数的变化规律。     

准连续TEM00模被动调Q Nd:YAG激光器的研究

采用峰值功率为500 W准连续激光二极管(LD)阵列侧面泵浦Nd:YAG晶体,Cr4+:YAG可饱和吸收体作为被动调Q元件,在重复频率为40 Hz时实现了单脉冲能量为8.24 mJ、脉冲宽度约7 ns的1 064 nm TEM00模调Q激光脉冲输出,脉冲峰值功率达到1.2 MW,从而为主振荡功率放大(MOPA)系统提供高峰值功率、高光束质量的种子源。对泵浦功率和泵浦脉冲宽度对输出脉冲特性的影响进行了实验研究。     

LDA端泵浦短腔Cr^4＋：YAG被动调Q Nd：YAG激光器

采用峰值功率600W的准连续（QCW）激光二极管阵列（LDA）端泵浦Nd:YAG晶体，其耦合装置为自制的微柱透镜阵列和透镜导管，使用Cr^4 :YAG可饱和吸收晶体作为Q开关，并选取长度较短的Nd:YAG晶体，从而使激光腔的长度缩短到11mm，实验研究了在较短的腔长条件下调Q输出多脉波形的时间、空间分布，采用平－平腔结构时，每次泵浦脉冲获得单脉冲输出，脉冲宽度＜4ns，能量4．5mJ。     

椭圆高斯分布半导体激光器泵浦被动调Q激光器的优化

在考虑泵浦光束和初始反转粒子数椭圆高斯分布的条件下，确定了新的调Q耦合速率方程。在椭圆高斯分布近似下，通过数值分析的方法针对脉冲能量进行优化，首次得到了归一化的脉冲能量和反射镜反射率等关键参数与无量纲变量z的关系曲线。文中以半导体激光器贴近端面泵浦，Cr4+:YAG作为饱和吸收体的Nd:YVO4被动调Q激光器为例进行了脉冲能量优化计算，在小信号透过率为75%，反射率91.8%时，对应最大脉冲能量1.5 J，峰值功率81 W，脉冲宽度18.4 ns。选用小信号透过率为73.4%的饱和吸收体和反射率为87%的反射镜进行实验验证，得到的脉冲能量为1.25 J，峰值功率为76.4 W，脉冲宽度为16.3 ns。理论计算与实验结果基本相符。     

LD侧面泵浦Nd:GdVO4电光调Q激光器研究

通过理论分析和实验研究,从泵浦效率、调Q性能、温度特性等几个方面比较了脉冲二极管泵浦NdGdVO4激光器和NdYAG激光器的差异;对NdGdVO4激光器采用侧面泵浦的方式,电光调Q得到了输出能量27.5mJ,脉冲宽度为6.4ns,泵浦效率远高于NdYAG激光器.     

掺铒铌酸锂调Q激光器的设计和分析

本文设计了用Mach-Zehnder干涉型调制开关作为调Q开关的掺铒铌酸锂（Er:LiNbO3）调Q波导激光器,并进行分析。发现激光器输出功率可达1.5kW以上;比较了泵浦光波长为980nm和1480nm时的输出功率和脉冲宽度的情况,研究了腔长变化对激光器输出特性的影响,发现用1480nm光泵浦时阈值较低,但用980nm光泵浦能得到更高的峰值功率和更窄的脉冲宽度。     

泵浦调Q的Nd3+∶YAG激光器输出特性研究

对泵浦调Q Nd3+∶YAG固体激光器进行了实验研究。分析了电光调Q的 Nd3+∶YAG激光器的输出特性。当泵浦电压从500~950V逐渐增大时,激光器单次脉冲能量逐渐变大,且满足近似线性变化关系;多次测量中稳定度从2.9%提高到0.5%;当泵浦电压从500~950V逐渐增大时,激光器的单次脉冲宽度逐渐变小,多次测量中稳定度从21.6%提高到10.5%;激光器的单次脉冲峰值功率近似线性增加。研究表明泵浦电压在700~900V时,激光器的单次脉冲能量和单次脉冲宽度比较稳定,稳定度分别近似为1%和13%。     

全光纤电光主动调Q激光器

利用马赫曾德尔Mach-Zehnder (M-Z)结构的尾纤型铌酸锂(LiNbO3)电光强度调制器作为Q开关元件,采用974nm半导体激光器作为泵浦源,峰值吸收系数为110dB/m的掺杂铒纤作为增益介质,实现了1550nm波长的全光纤主动调Q激光器。通过电光强度调制器对腔内损耗进行周期性调制,实现Q开关作用,获得了稳定的调Q脉冲输出。实验中通过改变泵浦功率和调制频率,研究了脉冲宽度和峰值功率的变化规律。获得输出脉冲重复频率50Hz-88kHz可调,重复频率1kHz时获得最窄脉冲宽度246ns,峰值功率近5W。     

LD侧面泵浦Nd∶GdVO4 电光调Q激光器研究

通过理论分析和实验研究,从泵浦效率、调Q性能、温度特性等几个方面比较了脉冲二极管泵浦Nd∶GdVO4 激光器和Nd∶YAG激光器的差异;对Nd∶GdVO4 激光器采用侧面泵浦的方式,电光调Q得到了输出能量27. 5mJ,脉冲宽度为6. 4ns,泵浦效率远高于Nd∶YAG激光器。     

泵浦调Q的Nd~(3+):YAG激光器输出特性研究

对泵浦调Q Nd3+:YAG固体激光器进行了实验研究.分析了电光调Q的Nd3+ :YAG激光器的输出特性.当泵浦电压从500-950V逐渐增大时,激光器单次脉冲能量逐渐变大,且满足近似线性变化关系;多次测量中稳定度从2.9%提高到0.5%;当泵浦电压从500-950V逐渐增大时,激光器的单次脉冲宽度逐渐变小,多次测量中稳定度从21.6%提高到10.5%;激光器的单次脉冲峰值功率近似线性增加.研究表明泵浦电压在700-900V时,激光器的单次脉冲能量和单次脉冲宽度比较稳定,稳定度分别近似为1%和13%.     

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.     

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.     

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.     

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.     

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