1 北京科技大学新材料技术研究院, 北京 100083
2 湘潭大学材料科学与工程学院, 湘潭 411105
金刚石以高导热率、强抗辐射性、高的电子迁移率等优异性能, 成为辐射探测器最合适的材料之一。探测器级的金刚石要求具有极低的杂质含量及位错密度等, 然而实际过程中同时实现杂质和位错的控制十分困难。本研究采用微波等离子体化学气相沉积(MPCVD)法, 通过前期的参数优化, 在最佳生长温度780 ℃、最佳甲烷浓度5%条件下, 在两个高质量高温高压(HPHT)金刚石衬底样品上进行了MPCVD金刚石生长, 并对衬底和生长层的氮杂质含量与缺陷结构进行了综合表征与分析。电子顺磁共振谱结果表明, 相比两个HPHT衬底样品的氮杂质原子百分数分别为7.1×10-6%和4.04×10-6%, MPCVD生长层的氮杂质原子百分数明显减少, 分别为2.1×10-7%和5×10-8%。由X射线摇摆曲线和白光形貌术测试结果发现, 尽管MPCVD生长过程中引入了部分位错, 使生长层应力增加, 畸变区域较多, 但总体位错与高质量衬底为同一数量级。本研究制备的高纯单晶金刚石有望应用于核辐射探测及半导体领域。
单晶金刚石 氮杂质 位错 白光形貌术 电子顺磁共振 single crystal diamond nitrogen impurity dislocation white light topography electron paramagnetic resonance
1 中国科学院上海光学精密机械研究所高功率激光物理重点实验室，上海 201800
2 中国科学院大学，北京 100049
3 上海交通大学IFSA协同创新中心，上海 200240
4 中国工程物理研究院上海激光等离子体研究所，上海 201800
拍瓦激光系统中剩余的高阶色散导致了脉冲波形的振荡，影响了拍瓦激光的信噪比。为了进一步优化拍瓦激光的信噪比特性，满足激光加速电子、质子等粒子的效率提升需求，本文提出了一种基于双折射晶体的新型超短脉冲的三阶色散主动调控方法，用于信噪比的主动调控。通过数值分析模拟了双折射晶体引入的二阶色散、三阶色散，针对中心波长为1053 nm的拍瓦激光系统，选择适当的晶体厚度，可以通过调节双折射晶体的面内旋转角改变系统剩余三阶色散。同时，基于神光Ⅱ第九路拍瓦激光系统光参量啁啾脉冲放大（OPCPA）预压缩的信噪比测量值，对比了不同量级剩余三阶色散对脉冲信噪比的影响，得出通过改变拍瓦激光系统中剩余三阶色散量，可实现不同量级信噪比的主动调控的结论。该研究结果对于高能激光系统剩余三阶色散的补偿以及信噪比的优化具有重要意义。
激光器与激光光学 双折射晶体 三阶色散 信噪比 拍瓦激光 光学学报
2023, 43(10): 1014003
Author Affiliations
Abstract
1 State Key Laboratory of Optoelectronic Materials and Technologies, School of Materials, Sun Yat-Sen University, Guangzhou 510275, China
2 State Key Laboratory of Intense Pulsed Radiation Simulation and Effect and Radiation Detection Research Center, Northwest Institute of Nuclear Technology, Xi’an 710024, China
3 School of Nuclear Science and Technology, Xi’an Jiaotong University, Xi’an 710049, China
4 CAS Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Key Laboratory of Nanomaterials, Fujian Institute of Research On the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China
5 School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China
Large-size scintillators with high efficiency and ultrafast radiation fluorescence have shown more potential in the applications to ionizing radiation detection of medical diagnosis, nuclear control and high-energy physics. Currently, although traditional scintillators have made tremendous progress in scintillation efficiency, there are still challenges left in fluorescence lifetime. Faced with that problem, we adopted 2-inch ZnO as the substrate and doped gallium as activator to realize an ultrafast fluorescence excited by α-ray, of which the decay time is only 600 ps that is the shortest scintillation decay time reported so far. The results show that the shallow donor related with gallium not only effectively suppresses band-edge self-absorption, but makes ultrafast radiation possible, which gets gallium-doped ZnO as a potential scintillator for high-quality ultrafast dynamic imaging proved.
Author Affiliations
Abstract
1 Key Laboratory for Laser Plasmas (MOE), Collaborative Innovation Center of IFSA, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, China
2 Joint Laboratory of High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, China
3 Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai, China
In strong-field physics experiments with ultraintense lasers, a single-shot cross-correlator (SSCC) is essential for fast optimization of the pulse contrast and meaningful comparison with theory for each pulse shot. To simultaneously characterize an ultrashort pulse and its long pedestal, the SSCC device must have both a high resolution and a large temporal window. However, the resolution and window in all kinds of single-shot measurement contradict each other in principle. Here we propose and demonstrate a novel SSCC device with two separate measurement channels: channel-1 for the large-window pedestal measurement has a moderate resolution but a large window, while channel-2 for the ultrashort pulse measurement has a small window but a high resolution; this allows the accurate characterization of the pulse contrast in a single shot. A two-channel SSCC device with a 200-fs resolution and 114-ps window has been developed and tested for its application in ultraintense lasers at 800 nm.
pulse contrast single-shot cross-correlator ultrashort ultraintense laser High Power Laser Science and Engineering
2022, 10(6): 06000e43
1 北京科技大学新材料技术研究院，北京 100083
2 北京科技大学顺德研究生院，佛山 528300
3 湘潭大学材料科学与工程学院，湘潭 411105
金刚石探测器具有体积小、抗辐照能力强、时间响应快等优点，在核辐射领域应用优势显著。早期金刚石核辐射探测器均采用天然金刚石材料，化学气相沉积(chemical vapor deposition, CVD)金刚石人工合成技术的进步，极大地促进了金刚石核辐射探测器的发展与应用。本文从CVD人造金刚石材料入手，分析了制约金刚石探测器性能的杂质与缺陷、CVD金刚石的合成工艺、探测器级金刚石中杂质与缺陷的表征方法，并基于载流子迁移率与寿命乘积、探测器的电荷收集效率等性能指标，总结了CVD金刚石中的杂质与缺陷对探测器性能的影响规律，介绍了国外金刚石核辐射探测器的应用现状并展望了国内金刚石核辐射探测器的发展前景。
金刚石 核辐照探测器 杂质 缺陷 载流子迁移率 能量分辨率 diamond nuclear radiation detector CVD CVD impurity defect carrier mobility energy resolution
Author Affiliations
Abstract
1 Key Laboratory of High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
2 Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
3 Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China
4 e-mail: liudean@siom.ac.cn
5 e-mail: oyxp@siom.ac.cn
A spectrum series learning-based model is presented for mode-locked fiber laser state searching and switching. The mode-locked operation search policy is obtained by our proposed algorithm that combines deep reinforcement learning and long short-term memory networks. Numerical simulations show that the dynamic features of the laser cavity can be obtained from spectrum series. Compared with the traditional evolutionary search algorithm that only uses the current state, this model greatly improves the efficiency of the mode-locked search. The switch of the mode-locked state is realized by a predictive neural network that controls the pump power. In the experiments, the proposed algorithm uses an average of only 690 ms to obtain a stable mode-locked state, which is one order of magnitude less than that of the traditional method. The maximum number of search steps in the algorithm is 47 in the 16°C–30°C temperature environment. The pump power prediction error is less than 2 mW, which ensures precise laser locking on multiple operating states. This proposed technique paves the way for a variety of optical systems that require fast and robust control.
Photonics Research
2022, 10(6): 06001491
1 上海科技大学物质科学与技术学院, 上海 200120
2 中国科学院上海光学精密机械研究所, 上海 201800
3 中国科学院大学材料与光电研究中心, 北京 100049
提出一种基于全光纤光谱干涉的多路超短脉冲大动态范围时间同步单次测量方法,弥补了非线性相关法测量同步状态时测量范围小和示波器测量时分辨率差的不足,解决了同步测量中空间光路的复杂性和单次实时测量的难题。首先对多路光纤阵列干涉测量进行仿真计算,然后设计四路脉冲传输的光路并在实验中验证多路同步单次测量方法的可行性,最后详细分析测量误差的来源和影响。该测量方法的最小同步时间精度为5.3 fs,测量范围为1.055~14.751 ps,与仿真结果有较好的一致性。该测量方法具有光纤链路易于集成、光谱干涉数据处理速度快、测量信号能量需求低等优势,在多路超短脉冲激光相干合束系统中有重要应用前景。
测量 同步测量 超短脉冲 光谱干涉 光纤阵列 单次测量 中国激光
2021, 48(16): 1604003
1 中国科学院上海光学精密机械研究所高功率激光物理联合实验室, 上海 201800
2 中国科学院大学, 北京 100049
3 中国工程物理研究院上海激光等离子体研究所, 上海 201800
提出一种标定超短脉冲测量装置时间分辨率的新方法。设计制作可产生特定时间延迟的平面平晶,标定时将其放置在自相关仪前的光路中;待测光脉冲经过平面平晶后会产生时间延迟为T的双脉冲,该双脉冲到达自相关晶体发生相互作用,产生自相关信号,此时信号的主峰两端会出现较为明显的次峰信号,该次峰信号之间的时间间隔为2T,这样双脉冲的时间延迟就转换为次峰信号峰值的空间距离,经CCD接收后可计算得到自相关仪的时间分辨率。采用此方法对自相关仪时间分辨率标定的结果为217.88 fs/pixel,与移动光程延迟器法得到的标定结果214.27 fs/pixel相比,相对误差仅为1.68%;与可单次标定的鉴别率板法相比,采用此方法标定结果的相对扩展不确定度为1.50%,优于鉴别率板法的6.96%。
Author Affiliations
Abstract
1 Department of Nuclear Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China
2 Shaanxi Engineering Research Center of Controllable Neutron Source, School of Science, Xijing University, Xi’an 710123, China
3 Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China
4 China Institute for Radiation Protection, Taiyuan 030012, China
5 Northwest Institute of Nuclear Technology, Xi’an 710024, China
Bulk scintillators that are with high density, low cost, and fine pulse-height energy spectral resolution, and are non-hygroscopic and user friendly, are desired for high-energy gamma-ray spectroscopy application. Recently, low-cost solution-processed perovskite nanoscintillators have been demonstrated with outstanding performances for indirect low-energy X-ray detection; however, the stability and thickness are not suitable for high-energy gamma-ray detection. Here, we report scintillation performances of a low-cost solution-processed bulk 0D single crystal. The self-trapped exciton emission results in a large Stokes shift (109 nm) that is reabsorption free. A broad X-ray excited emission matches well with the sensitivity of a silicon photodiode. The unique surrounded isolated cluster scintillator provides ultra-stability in air and strong radiation hardness under high-dose gamma-ray exposure from a 60Co source. This solution-processed scintillator is expected with low-cost and has detection performances comparable to commercial alkali-halide scintillator products.
Photonics Research
2021, 9(3): 03000351
1 中国科学院上海光学精密机械研究所高功率激光物理联合实验室, 上海 201800
2 中国科学院大学材料与光电研究中心, 北京 100049
高功率超短脉冲激光系统中,空间滤波器透射元件引入的色差会影响系统的聚焦功率密度。针对这一问题,提出一种具备动态调节能力的色差预补偿方案。该方案由正负透镜和反射系统构成共焦像传递系统,能够实现全系统色差的动态精确补偿。基于该方案为神光-II 5 PW(SG-II 5 PW)激光系统设计并搭建了色差预补偿光路。实验结果表明,通过精密调节该单元内部透镜间距能够精确补偿全系统的色差,显著提升系统峰值功率密度。经过色差补偿后,在SG-II 5 PW系统开展质子加速实验,获得了超过16 MeV的质子产额。
激光光学 高功率超短脉冲激光 宽带激光 空间滤波器 色差 传输时间延迟
