大口径深焦比Hindle球面镜曲率半径精确测量

Hindle法无像差法检测凸双曲面中,大口径深焦比球面反射镜的曲率半径测量是关键技术之一。提出了一种基于激光干涉仪、三坐标测量臂及标准定标球相结合测量球面曲率半径的方法。在球面镜面形干涉检验光路中引入一个标准定标球体,将其球心与检测系统的焦点重合,应用FARO测量臂对标准定标球体球心和被检球面镜镜面点坐标进行采样,从而计算球面镜曲率半径值。对一个口径Φ800 mm、设计半径为861.8 mm的球面标准反射镜进行曲率半径测量及精度分析,实测曲率半径为862.036 mm,系统的最大测量误差为±0.036 mm,测量不确定度为±0.015 mm;经Zemax软件分析,该测量误差对双曲面检测精度的影响仅为精度要求的3.4%,验证了这种球面半径测量方法的有效性及实用性。     

燃料元件功率瞬变试验调节装置

通过建立功率调节装置来实现PWR燃料元件在瞬态试验中的功率变化要求，调节装置由驱动机构、固体中子吸收体、控制系统组成，在堆外对装置机械部分、控制系统部分进行调试试验。调试结果表明调节装置运转顺利，控制系统能满足吸收体以不同的速度上下运动的要求，同时在事故情况下可停止吸收体的运动。     

超大型地面天线辐射特性实地测量技术

针对口径超过 10 m 的超大型地面天线由于极高成本难以进行精确测量的难题,提出了基于无人机的平面近场实地测 量方法。 首先对无人机散射、定位精度及测量场区选择等影响天线实地测量结果的主要因素进行了仿真分析,确定了测量区 域。 采用多旋翼无人机和高精度飞控技术,在高性能无人机最好 20 mm 飞控精度、5 mm 测量精度的条件下,进行了天线实地测 量系统的射频链路设计,并给出了两种近远场数据变换方法,可以有效解决在较高频段无人机定位精度差导致测量结果不可信 的问题。 采用实例分析验证了方法的有效性,为超大型地面天线低成本精确测量提供了较好的解决途径。     

同位素热源量热方法研究

为了解决放射性同位素核源的热功率测试需要,进行了同位素核源量热方法的研究,通过搭建热功率测试试验装置,对各种影响量热精度的因素进行了分项试验、计算分析.试验结果表明,基于Gardon型热流传感器原理的量热方法,对于基本测量对象,用厚度为1.0 mm的康铜片作为敏感部件,可以实现在120～ 130W热功率范围内测试误差不大于1％,由试验研究分析表明测量原理可行,满足对同位素热源的量热精度要求.     

激光等离子体引导空气间隙放电的实验研究

为推进激光引雷技术的实用化进程,文中开展了激光等离子体引导间隙放电的实验研究。采用Nd:YAG固体脉冲激光器电离空气产生一定浓度的等离子体通道,等离子体通道作用于施加一定电压的极板间的空气间隙,进而引导空气间隙的击穿放电。搭建了激光引导间隙放电的实验平台及测量系统,开展了不同激光能量(200、400 m J)及激光波长(532、1 064 nm)引导下间隙放电的实验研究,获得了不同参数激光等离子体对空气间隙击穿特性的影响规律。实验结果表明空气间隙击穿阈值电压随着激光能量的增大而降低并逐步趋于饱和,在相同输出能量下532 nm激光可更有效地降低空气间隙击穿阈值电压。研究结果为激光引雷技术的发展及应用提供了实验依据。     

电力电子模块封装硅胶电荷输运与陷阱特性研究

高压功率模块封装绝缘承受单极性的电应力,而高压功率模块封装绝缘中的空间电荷问题却没有得到足够的研究。本文研究了封装硅胶材料在不同温度下的空间电荷输运行为和陷阱能态分布特性。基于研发的空间电荷与陷阱能态联合测量系统,在 3～15 kV/mm的外施电场和 40、60、80℃温度下对封装硅胶进行空间电荷和等温松弛电流联合测量...     

应用光电倍增管模块的杂光系数测试与分析

为提高杂光测试系统集成度和测试精度,采用新型光电倍增管模块作为探测器进行杂光系数测试,并研究了测试过程中的数据采集、滤波、计算方法。首先描述了黑斑法测试杂光系数的原理,在此基础上介绍了测试系统工作原理和组成。分析了系统噪声干扰来源,并利用功率谱对噪声信号进行了描述、分析。为降低噪声干扰,对输出信号进行了低通滤波和数据均值处理。对某80~400 mm变焦镜头进行了杂光系数测试实验。当焦距400 mm时,杂光系数均值为2.623%,均方根误差0.019%;焦距80 mm杂光系数均值为1.829%,均方根误差0.02%。实验表明该杂光测试系统具有较高的测量精度和重复精度,满足黑斑法杂光系数重复测量精度要求。     

T2低气压Ar—Hg放电正柱的辐射效率测量

在冷端温度20～80℃,放电电流20～200mA的工作条件下,测量了充400Pa氩（Ar）的T2低气压Ar—Hg放电灯（外径7mm）正柱中波长为254nm的辐亮度和电场强度。通过测量不同温度、不同电流下的Koedam系数,计算出了254nm辐射功率。结果表明,T2灯254nm辐射的最佳冷端温度在50℃左右,正柱的电能转换在254nm时的辐射效率为48％～56％。     

多谱线TDLAS测温中谱线选择的实验研究

采用可调谐半导体激光吸收光谱技术,利用两条谱线可以测量激光路径上的平均温度。在利用多条谱线测量激光路径的平均温度时,测量的精确度主要受制于测量信号的离散程度以及谱线低能级能量的分散程度。利用中心波长为1392.5 nm(7181.32 cm~(-1))的激光器快速扫描4条H_2O的波数为7182.950、7182.209、7181.156、7179.752 cm~(-1)的吸收谱线,研究了不同的谱线组合方式对激光路径平均温度测量精密度的影响。实验结果表明,进行谱线选取时,通过依次去掉一条谱线并计算其余谱线测量标准偏差的结果,能够快速反映出被去掉谱线对温度测量精确度的权重。通过谱线选择,测量得到的路径上平均温度的标准偏差小于20 K。     

脉冲电压下尼龙的激光触发沿面闪络特性

为研究脉冲电压下的激光触发沿面闪络特性,在试验系统中建立了精确的激光触发沿面闪络试验系统,解决了激光脉冲与试品上所加脉冲电压的同步问题,在此基础上应用平板电极和柱状尼龙绝缘材料进行了激光触发沿面闪络试验。试验中采用60 mm直径的铜材料平板电极,试品为20 mm直径、6、8、10 mm厚的尼龙材料圆柱绝缘材料,试验中激光波长为10645、32 nm并聚焦成2 mm×30 mm的长方形光斑,得到在不同的激光能量密度及施加电压下的闪络时延和抖动时间,并探讨了激光触发沿面闪络的机理。研究表明:激光能量密度越大、施加电压越高,闪络时延和抖动时间越小。     

High-power mode-locked external cavity semiconductor laser usinginverse bow-tie semiconductor optical amplifiers

This paper presents experimental results of using an inverse bow-tie gain guided semiconductor optical amplifier (SOA) as the optical gain element in a high-power external cavity semiconductor laser. An average output power of 700 mW is demonstrated in continuous-wave (CW) operation while 400 mW of average power is obtained in both passive and hybrid mode-locked operation, with subsequent optical amplification in an identical SOA. The mode-locked laser operates at a repetition rate of 1.062 GHz, owing to the interplay between the gain and saturable absorber dynamics. Optical pulses are generated with a temporal duration of 5 ps, which implies a pulse energy of 376 pJ, and a peak power of 60 W. Further reduction of the optical pulsewidth to 1.3 ps is also achieved by using dispersion compensation techniques. These results show the promise of novel SOA devices for use as gain elements in external cavity semiconductor lasers. The generated output pulse characteristics from mode-locked operation is sufficient for use in novel three-dimensional data storage applications, and in large-scale commercial printing and marking applications     

Laser-diode end-pumped passively Q-switched intracavity-frequency-doubling Nd:GdVO/sub 4//KTP Green laser with GaAs saturable absorber

The intracavity photon density is assumed to be Gaussian spatial distributions, and the nonlinear loss that is due to second-harmonic generation (SHG) to the photon-density equation is given under Gaussian spatial distributions in the rate equations for a laser-diode end-pumped passively Q-switched intracavity-frequency-doubling Nd:GdVO/sub 4//KTP laser with a GaAs saturable absorber. These space-dependent rate equations are solved numerically. The dependences of pulsewidth, pulse repetition rate, single-pulse energy, and peak power on incident pump power are obtained for the generated-green-laser pulses. In the experiment, a laser-diode end-pumped passively Q-switched intracavity-frequency-doubling Nd:GdVO/sub 4//KTP laser with a GaAs saturable absorber is realized, and the experimental results are consistent with the numerical solutions.     

Effect of Peak Power and Pulse Width on Coherent Doppler Wind Lidar''s SNR

The laser device is the core component of coherent Doppler wind lidar. The peak power and pulse width of laser transmitting pulse have important effects on SNR. Based on coherent Doppler wind pulse lidar, the peak power and pulse width influence on SNR is studied on the theoretical derivation and analysis, and the results show that the higher the peak power can realize the greater the signal-to-noise ratio of coherent Doppler wind lidar. But when the peak power is too large, the laser pulse may appear nonlinear phenomenon, which cause the damage of the laser. So, the peak power must be less than the stimulated brillouin scattering power threshold.Increasing the pulse width can make the laser device to output more energy, but it will also make the spatial resolution lower, and the influence of turbulence on SNR will be greater. After a series of simulation analyses, it can be concluded that when the peak power is 650W and the pulse width is 340ns, the SNR of the system can be maximized. In addition, the coherent Doppler wind lidar system is set up to carry out corresponding experimental verification. The experimental results are consistent with the theoretical analysis and simulation, which verifies the correctness of the theoretical analysis and simulation results. It provides theoretical basis and practical experience for the design of laser transmitting pulse in coherent Doppler wind lidar system.     

Ozone production using pulsed dielectric barrier discharge inoxygen

The production of ozone was investigated using a dielectric barrier discharge in oxygen, and employing short-duration pulsed power. The dependence of the ozone concentration (parts per million, ppm) and ozone production yield (g(O₃)/kWh) on the peak pulsed voltage (17.5 to 57.9 kV) and the pulse repetition rate (25 to 400 pulses/s, pps) were investigated. In the present study, the following parameters were kept constant: a pressure of 1.01×10⁵ Pa, a temperature of 26±4°C a gas flow rate of 3.0 1/min and a gaseous gap length of 11 mm. A concentric coaxial cylindrical reactor was used. A spiral copper wire (1 mm in diameter) was wound on a polyvinylchloride (PVC) cylindrical configuration (26 mm in diameter) and placed centrally in a concentric coaxial electrode system with 4 mm thick PVC dielectric layer adjacent to a copper outer electrode of 58 mm in internal diameter. HV and current pulses were provided by a magnetic pulse compressor power source     

Self-starting 6.5-fs pulses from a Ti:sapphire laser using asemiconductor saturable absorber and double chirped mirrors

We demonstrate self-starting 6.5-fs pulses from a Kerr-lens-mode-locked Ti:sapphire laser with an average output power of 200 mW at a pulse repetition rate of 86 MHz. We have achieved a mode-locking buildup time of only 60 μs, using a broad-band semiconductor saturable absorber mirror to initiate the pulse formation. The dispersion has been compensated with a prism pair in combination with improved double-chirped mirrors. The prism pair allows for the flexible adjustment of both the duration and the center wavelength of the pulse. The double-chirped mirrors show a high reflectivity better than 99.8% over the full bandwidth of 300 nm and a controlled group delay over more than 250 nm. The choice of a proper output coupler turns out to be critical for ultrashort pulse generation directly from the laser     

大功率超高速半导体开关的换流特性研究

研究了一种应用于激光驱动源的大功率超高速半导体开关反向开关晶体管(RSD)的新结构，以实现ms、ns脉宽、MW以上的高重复率脉冲的产生和控制。RSD具有大面积快速均匀开通、可无限串联、功率大、换流效率高、寿命长的特点。利用单次脉冲试验平台研究了RSD的开通机理及高密度能量转换、允许通过的峰值电流、开通条件与预充、准静态损耗及其di/dt等多项特性。根据经验公式，对小直径RSD做极限电流试验，f 20mm的RSD堆体通过了19.9kA脉冲电流(脉宽30ms)。通过减小主回路电感考核了RSD的高di/dt 耐量特性，放电电压3kV时得到di/dt接近8kA/ms。     

Picosecond SESAM-based ytterbium mode-locked fiber lasers

Using semiconductor saturable absorber mirrors and a grating-pair dispersion compensator, we obtain reliable self-starting mode locking of a ytterbium (Yb) fiber laser tunable over 125 nm. The 980-1105-nm tuning range is achieved by optimization of nonlinear reflection and bandgap characteristics of the multiple-quantum-well saturable absorber and by proper engineering of the laser cavity. A short-length Yb-doped double-clad amplifier seeded with mode-locked Yb-fiber laser produces picosecond pulses with energy of 30 nJ (700 mW of average power). A compact version of the fiber laser was built using a Gires-Tournois compensator and short length (1-cm long) of highly doped Yb fiber. Using a novel semiconductor saturable abserver mirror based on GaInNAs structure, self-started 1.5-ps pulse mode-locked operation was obtained at 1023 nm with a repetition rate of 95 MHz. A mode-locked Yb-doped fiber laser was also developed without using any dispersion compensation technique. Overall group-velocity dispersion was minimized by using highly doped Yb fiber in a compact amplifying loop cavity. Self-started mode-locked operation was obtained in 980-1030-nm wavelength range with a fundamental repetition rate of 140 MHz. Without using dispersion compensation, the lasers produced pulses in a range from 15 to 26 ps.     

High Peak Power Pulse Amplification in Large-Core Yb-Doped Fiber Amplifiers

High peak power fiber lasers are important for a variety of applications ranging from material processing and remote sensing to laser-plasma produced extreme ultraviolet lithography (EUV) generation. These applications require high peak powers in the megawatt range, < 1-10-ns pulse durations and high average powers in preferably diffraction-limited beams. In this paper, we review our work on high peak power pulse generation using large- mode-area (LMA) Yb-doped fibers with very large cores. We report achieving up to > 5-MW peak power with subnanosecond pulses, the highest peak power achieved so far from a fiber laser. Use of a variety of core sizes between 65 and 200 mum has been explored and it has been shown that for core sizes as large as 80 mum, a good output beam quality of M² ~ 1.3 can be maintained. This corresponds to the largest ever demonstrated mode area (2750 mum²) of a conventional LMA fiber with nearly diffraction-limited output. We also demonstrate average-power scaling of megawatt peak power pulses of up to ~90 W.     

Superhigh-power picosecond optical pulses from Q-switched diodelaser

Generation of 40-ps optical pulses was demonstrated with a peak power of up to 45 W in a single mode and of up to 380 W from a broad-area laser diode. Such optical power was achieved in the Q-switching regime by means of a saturable absorber formed inside the laser cavity by deep implantation of heavy ions     

大功率半导体激光器脉冲式恒流驱动电路设计

针对半导体激光器驱动电路的脉冲式恒流需要,提出了一种以金属氧化物半导体场效应晶体为开关器件,采用了闭环反馈系统,运用负反馈原理输出恒定电流的半导体激光器驱动电路。为了防止过冲电压和纹波造成半导体激光器的损坏,在电路的设计中加入了限流保护电路并且使用了高摆率的运放。经测试,消除了过冲电压,实现了脉冲恒流的输出,实际应用表明该脉冲恒流源驱动电路对激光器安全可靠,峰值功率可达40 W。