高增益的类Ne锗软X光激光实验

采用新颖的“双靶对接”设计,利用强度约12×10^(13)W/cm^2,波长1.05μm,脉宽约1ns的两路激光线聚焦辐照平面厚锗双靶,观察到了波长为19.6、23.2、23.6、24.7和28.6nm的五根类Ne锗3p-3s跃迁谱线的放大。波长为23.2和23.6nm的谱线,增益-长度乘积GL的值约13。利用软X光扫描相机观测了四根软X光谱线的时间特性。     

类氖锗X光激光增益实验

本文介绍了在LF-12激光器上进行的类氖锗X光激光增益实验。当泵浦激光波长为1.053μm,脉宽为1.1～1.4ns、能量为550～650J、线聚焦焦斑为185μm×20mm时,使用片状锗靶测量波长为19.61、23.22、23.63、24.73及28.65nm的五条激光跃迁线的增益分别为3.06、3.99、3.72、2.36及4.59cm^(-1)。实验给出了关于柱形等离子体激光介质发射区厚度及软X射线激光发射角的实验数据。实验也给出了软X射线激光强度随泵浦激光功率密度变化的讯息。最后分析了由薄膜锗X光激光靶进行的增益实验中未看到激光增益线的原因。     

反射镜多靶串接增益饱和软X光激光实验

利用Mo/Si多层膜软X光反射镜实现了类氖锗软X光激光的双程放大,在顺接双靶总长28mm时,加与不加反射镜相比,软X光激光输出强度增强了40倍左右,已接近饱和;光束发散角减小,增益区厚度变薄,光束的空间相干性改善。当串接四靶总长为56mm时,加与不加反射的软X光激光输出强度没有明显的差异,表明已达到深度的增益饱和。     

类氖锗等离子体中软X激光饱和增益实验研究

进入“冰窗”波段和获得饱和增益输出是当前实验室研究X激光的目标。考察X激光输出的强度随靶长的变化规律,是判断是否达到饱和增益的重要依据,但必须排除折射等因素造成的假像。为了校正折射等的影响,我们曾经提出并实施了“双靶对接”方案,在功率为10~(12)W的LF-12~#钕玻璃激光装置上,获得了高增益的类氖锗等离子体中软X激光输出。最近,在饱和增益研究实验中,我们发展了双靶对接的概念。设计了“多靶串接”方案,获得了趋于饱和的类氖锗等离子体中软X激光输出。     

平面孔靶激光等离子体堵口

以波长为1.06μm的强激光束辐照金平面孔靶,在小孔边缘激光功率密度I为8.3×10~(12)Wcm~2—4.8×10~(13)W/cm~2条件下,由高速摄影获得的堵口图象,推得堵口速度c_T为4.5×10~(?)cm/s—1.0×10~(?)cm/s,定标式为c_T=101(?)。还研究了时间积分的能量透过率。它依赖于小孔直径、激光脉宽和激光能量等。实验还发现,孔靶等离子体X光辐射时间呈双峰特征、空间分布出现 形状的图象。     

柱状锗等离子体状态的时空分辨诊断

在四靶串接X光激光实验中,用时间分辨晶体谱仪记录了类Ne锗共振线及其类Na伴线的时间扫描特性。测出了这些谱线的辐射持续时间(FWHM)约为0.95ns。考察了锗等离子体电子温度T_e随时间的演化,观测到T_e≥400eV的维持时间大于1.2ns。用空间分辨晶体谱仪诊断得到锗等离子体电子温度T_e和电子密度n_e的轴向分布,其平均值T_e=4.9×10~2eV,n_e=1.2×10~(20)/cm~3。     

提高X光激光相干性的镶嵌靶的研究

 在以锗等离子体为增益介质的X光激光实验研究中，使用铜锗镶嵌靶可以获得一维横向宽度很窄的柱状等离子体，这有利于X光激光的单横模输出。本文对铜锗镶嵌靶进行了实验研究。     

低强度激光泵浦类Ni离子X光激光实验

 在试运行的神光Ⅱ装置上,采用新设计的凸柱面透镜列阵均匀线聚焦系统, 用两束激光焦线叠加和双靶对接等技术,以预主脉冲激光驱动方式,在(5～8)×10¹³W/cm²的较低强度激光泵浦条件下,观测到Ni-like　Dy、Er、Yb的软X光激光输出,测得波长5.02nm类Ni-Yb和波长5.86nm类Ni-Dy的软X光激光的增益系数分别为1.6cm^-1和1.4cm^-1     

基频光腔靶辐射温度定标

研究腔靶辐射温度和X光耦合效率与靶结构及激光辐照条件的依赖关系。利用神光-Ⅱ基频光(波长1．053μm,能量3～5kJ／8束,脉宽0．6～0．9ns)辐照金腔靶。采用软X光能谱仪及平响应探测器分别测量腔靶诊断口辐射X光功率谱及其能量角分布。同时,利用五针孔时、空分辨成像技术对腔靶诊断口发射软X光进行实验观测,给出辐射温度推算中需要的等效诊断口面积修正因子。在北京同步辐射软X光标定站,对上述诊断用软X光探测元器件进行了全谱范围(0．05～1．5kev)的绝对标定,以提高X光辐射功率和黑腔辐射温度的诊断精度．     

19.6nm波长类氖锗X光激光光源理论模拟

 波长19.6nm的类氖锗X光激光适合作为诊断激光等离子体界面不稳定性的光源。用经过实验检验的系列程序对预-主短脉冲驱动类氖锗进行了系统的优化设计和理论分析。采用2%~3%的预脉冲强度，6~8ns的预-主脉冲时间间隔，在4×10¹³W/cm²功率密度驱动下, 波长19.6nm增益区的宽度可以超过60μm，增益区的维持时间可以达到90ps。对于16mm长的平板靶，增益系数可达11.8/cm；弯曲靶增益系数可达13.3/cm；单靶小增益长度积可达21.3，单靶就可以获得饱和增益。采用双靶对接，其小讯号增益可达38.4，可以获得深度饱和增益，能满足应用演示所需的X光激光光源。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.