Si/SiGe量子级联激光器的能带设计

详细论述Si/SiGe量子级联激光器的工作原理，通过对比找到一组合适的Si，Ge和SiGe合金的能带参数，进而应用6×6 k·p方法计算了不同阱宽、不同Ge组分Si/Si_1-xGe_x/Si量子阱价带量子化的空穴能级本征值及其色散关系，分析Si/Si_1-xGe_x/Si量子阱空穴态能级间距随阱宽和组分的变化规律，最后应用计算结果讨论了Si/SiGe量子级联激光器有源区的能带设计，有益于优化Si /SiGe量子级联激光器结构. 关键词： 硅锗材料 量子级联激光器 子带跃迁 k·p方法')" href="#">k·p方法     

Electron Energy Distribution Function Extraction Using Integrated Step Function Response and Regularization Methods

Recently, electron energy distribution function (EEDF) extraction techniques have been evaluated using regularized solutions to the integral problem. These techniques do not assume any mathematical representation of the EEDF and solve the integral problem for any function that best represents the EEDF. Also, unlike the more widely used point-by-point extraction of the second-derivative relationship, the integrated relationship between electron current and the EEDF is used, instead of a relatively small fraction of the integrated data in the point-by-point method. In this paper, the electron current for an arbitrary distribution function is derived, assuming that the distribution is a sum of step functions representing such a function. This technique for EEDF extraction is validated by adding noise to numerically generated data and using a regularized least squares (RLS) method to calculate the original function by solving for the individual step function contribution to the total electron current. Comparisons are then made between the expected and the reconstructed solution to evaluate its accuracy with respect to EEDF reconstruction and integrated normalization of the electron density.      

具有时间分辨能力的高能强流电子束光学渡越辐射测量系统

光学渡越辐射作为高能强流电子束束流参数测量的一种方式, 具有时间响应快、分辨率高等特点, 可以测量电子束的束剖面、发散角、能量等多个参数；通过电子束束参数的时间分辨测量则能够了解电子束产生、运输中的问题, 非常有利于加速器的研究与调试. 一种具有时间分辨能力的、利用光学渡越辐射进行高能强流电子束参数测量的系统被建立起来, 并应用到了18.5MeV, 2.5kA, 90ns的实际的电子束束参数的在线测量中, 具有以10ns的时间间隔和3ns的曝光时间来获得90ns内相应的时间分辨的束发射度的变化值的能力, 为加速器的研究提供了又一个强有力的测试手段. 该系统具有的时间分辨能力最高到达10ns, 一次可以拍摄到8幅图像, 最小的曝光时间为3ns, 图像分辨率为1376×1035, 幅面可以达到φ80mm以上.     

A Noteworthy Trap in Using the EDC Method for Solving Dielectric Waveguide Problems

EDC method is probably the simplest method to obtain a good approximation for the propagation constant of a dielectric waveguide. It is well know that there are two ways to perform the EDC procedure: one is to treat the LSE mode first then the LSM mode and the other is just reverse. It is true that the difference between the results got from the two ways is usually rather small and thus both of them are good approximations. In this paper, we show that in some cases the two ways will lead to much different results; one is still a good approximation while the other is completely unacceptable. The theoretical analysis tells us that if performing the LSM mode first then with the LSE mode will usually get a good result.     

Ground State Energy for Fermions in a 1D Harmonic Trap with Delta Function Interaction

Conjectures are made for the ground state energy of a large spin 1/2 Fermion system trapped in a 1D harmonic trap with delta function interaction. States with different spin J are separately studied. The Thomas-Fermi method is used as an effective test for the conjecture.     

采用加权直方图分析和蒙特卡洛重采样法对自由能级的校正研究

本文采用加权直方图分析方法和蒙特卡洛重采样方法进行自由基校正研究. 生成的自由能表面几乎可以收敛到具有足够采样情况的精准表面,并且比常规的加权直方图分析校正方法能更稳定地处理采样不足的情况,为检测能级校正表面的不确定性提供指南,并且定义了明确的标准用以确定能改善其视觉效果的自由能表面平滑程度. 本文通过水中的丙氨酸二肽和KillerRed蛋白质子转移的自由能图证明该方法的优势,说明蒙特卡洛重采样法可以作为在产生自由能表面实际的系统中的实用工具.     

邻氟苯甲酸铽配合物的制备及其能级匹配程度研究

为了研究配体能级与稀土离子最低激发态能级的匹配程度对所形成的稀土配合物荧光性能的影响,以邻氟苯甲酸(2-FBA)为第一配体,邻菲咯啉(phen)为第二配体分别制备两种稀土铽配合物Tb(2-FBA)_3·2H_2O和Tb(2-FBA)_3phen。元素分析和红外光谱表征了两种配合物的分子组成。相同浓度的紫外吸收光谱表明,Tb(2-FBA)_3phen的第二配体phen替代第一配体2-FBA吸收了部分紫外光。相同浓度的液体荧光光谱表明,Tb(2-FBA)_3·2H_2O的荧光发射强度高于Tb(2-FBA)_3phen的荧光发射强度。由于Tb(2-FBA)_3·2H_2O分子结晶水中的O—H振动会大大消耗配体所吸收的能量而使荧光强度大幅度下降;2-FBA配体在273 nm的吸收峰所对应的三重态能级必然与能级~5D_4的匹配程度会更差。在这种情况下Tb(2-FBA)_3·2H_2O的发射强度依然高于Tb(2-FBA)_3phen的发射强度,充分说明了第一配体2-FBA与Tb~3的最低激发态能级~5D_4的匹配程度要好于phen与Tb~(3+)的最低激发态能级~5D_4的匹配程度。通过结合紫外吸收光谱和荧光光谱对稀土配合物的配体能级的定性分析,可以初步了解不同类型配体对荧光性能的贡献程度。     

双光子过程的能级图和时序图

从辐射与分子相互作用的跃迁几率幅出发,说明各种双光子过程的能级图和时序图与相互作用的微扰矩阵元的对应关系。     

强流ECR离子源引出系统研究

为了提高强流ECR 离子源的引出束流品质,分别设计了1# 和2# 引出系统,利用束流引出模拟软件PBGUNS 对1# 和2# 引出系统进行了质子束流引出与传输的模拟计算,结合实际测得的发射度数据分析引出系统,发现2# 引出系统比1# 引出系统引出束流品质高。对ECR 离子源引出系统的电势等位线分布等参数引起的球差进行了简单数学推导及MATLAB 绘图,并结合1# 和2# 引出系统束流相图模拟结果证明了球差会使引出束流品质有效发射度增长,通过适当加大电极孔径可改善束流聚焦情况,得到了束流光学聚焦较好的束流引出系统设计。To improve the quality of extracted ion beam from a high current ECR ion source, 1# and 2# extraction systems were designed and tested. The PBGUNS code was used to simulate the 1# and 2# extraction systems of proton ion beam. The emittance measurement results with the two different extraction systems were compared and analyzed with the simulation, the conclusion that more high quality beam extracted from 2# system than 1# system was got. The formula derivation of ECR ion source extraction system spherical aberration and MATLAB drawing was done by the analyzing on the distribution of extraction field equipotentials, effective emittance increasing caused by spherical berration was proved by 1# and 2# extraction systems beam phase space simulation result, beam focusing would be improved if electrode hole size increasing appropriately and a general concept on good optics focusing of ion beam extraction system was proposed finally.     

用于原子能级结构研究的激光共振电离光谱系统

激光共振电离光谱技术是一种利用一路或多路激光将待测原子选择性共振激发与电离,通过测量离子信号来研究原子能级结构的光谱技术。研建了一套激光共振电离光谱装置,用于原子高激发态能级结构参数的测量。分别从该装置的总体结构、关键技术和应用实例等方面进行了详细介绍。该套装置主要包括高调谐精度的染料激光器系统、高效的激光离子源系统和高分辨率的飞行时间质量分析器。染料激光器系统包括3台多纵模可调谐染料激光器和1台单纵模可调谐染料激光器,均为脉冲工作方式,重复频率为10 kHz,泵浦源均为532 nm的Nd∶YAG固体激光器。激光离子源系统包括原子化源、激光与原子相互作用区和离子光学透镜组三部分组成,样品在原子化源中被电加热实现原子化,喷射出的原子被激光选择性激发、电离,产生的离子被离子传输透镜整形成能量分散小、束窄的离子束。飞行时间质量分析器采用了反射式结构设计、脉冲垂直推斥技术和偏转板调节技术。利用此装置,实验测定了U原子的自电离态光谱,获得了U原子一条较佳的三色三光子共振电离路径,对应激光的波长分别为591.7,565.0和632.4 nm。此系统还可用于测量同位素位移和原子超精细结构等参数。另外,由于此系统中联用了质量分析器,因此可用于样品多元素分析、痕量元素分析、同位素丰度分析。     

带有质量分析系统的强流质子束低能传输线研究

强流质子源与低能传输线（LEBT）是作为CIADS注入器的超导强流质子直线加速器的关键前端系统。目前LEBT采用双螺线管匹配结构设计,并安装有限制锥,但仍然不能避免少量H₂+和H₃+进入后端加速装置,这对直线加速器长期运行稳定性与可靠性会产生一定影响。为此,在LEBT加入分析磁铁对混合束（H+,H+2,H₃+）进行分离再注入后端加速器腔体,将是一个有效的方案。本研究对经过带有30度分析磁铁的LEBT的强流质子束的束流品质进行了模拟与实验测量。结果表明,分析磁铁高阶磁场的影响使经过分析磁铁的强流质子束束流品质变差,并且该影响随着束流包络的增大而增大。这些结果为CIADS注入器的低能传输线设计提供了参考依据。High current proton source and the low energy beam transport(LEBT) are the key front-end systems for CIADS injector:high current proton linac accelerator. CIADS injector's LEBT adopts double solenoid matching structure, using a limit cone which can partially avoid H₂+ and H₃+ which injecting into the back-end linac accelerator may impact the long-term stability and reliability of the whole system. It will be an effective method to separate the hybrid ions (H+, H₂+, H₃+) by adding a dipole magnet at LEBT. In this article, we simulated and mesasured the high current proton beam quality behind the LEBT with a 30 degree dipole. The results show that the the proton beam quality is significantly effected by high-order magnetic fields of the dipole magnet, and the effect increases with the increase of the beam envelope. The achieved result is useful for the LEBT design of CIADS injector.     

Analysis of Possible Evolution of Dark Energy by Using a Power Series

We simulate the density of dark energy by using a power series to analyse the possible evolution of dark energy. The parameters are constrained from the newly released Cold sample of the supernova dataset. The evolutions of dark energy, as the power series from two free parameters to five free parameters, have the common and the different characters. We may conclude that either the density of dark energy possibly oscillates or increases after it decreases to a minimum value. Accordingly, the state equation of dark energy oscillates or evolves from ωde〉 -1 in the past to ωee〈 -1 around the present epoch.     

Novel Technique for All-Optical Clock Extraction Using Fiber Bragg Gratings

We demonstrate a simple passive technique, using phase shifted fibre Bragg gratings, for extraction of optical clock signals from RZ optical data signals . The generation of an optical clock signal at 12.5 GHz from a 12.5 Gbs RZ optical data stream is experimentally demonstrated with simulation of optical clock extraction at 10 GHz fro m 40 Gbs OTDM data streams .     

基于光学沃尔什变换特征提取的图像匹配

采用光电结合的方法实现了沃尔什 （Walsh）分量变换,提出出反映图像主要特征的分量,用于大容量图像库的内容匹配查找,基于以非相干光相关器为核心的光电混合图像处理系统,实现了基于光学沃尔什变换特征提取的图像匹配算法。     

Sea Level Muon Spectrum Derived from Bugaev Model Using the Primary Cosmic Ray Energy Spectrum of Grigorov et al

In a recent paper BHATTACHARYYA has derived the pion and kaon production spectra in the atmosphere using a form of the primary nucleon energy spectrum of the measurements of GRIGOROV et al. and the interaction model of BUGAEV et al. The sea level muon spectrum derived from these meson spectra agrees with the magnetic spectrograph data of ALLKOFER et al. and AYRE et al. In this report a critical analysis of the paper has been made and some obvious mistakes in the formulation have been pointed out. The formulation of BUGAEV et al. and the data of GRIGOROV at al. have been misinterpreted by BHATTACHARYYA . The corrected results have been properly interpreted in this report.     

Blind Extraction of Chaotic Signals by Using the Fast Independent Component Analysis Algorithm

We report the results of using the fast independent component analysis （FastICA） algorithm to realize Mind extraction of chaotic signals. Two cases are taken into consideration： namely, the mixture is noiseless or contaminated by noise. Pre-whitening is employed to reduce the effect of noise before using the FastICA algorithm. The correlation coefficient criterion is adopted to evaluate the performance, and the success rate is defined as a new criterion to indicate the performance with respect to noise or different mixing matrices. Simulation results show that the FastICA algorithm can extract the chaotic signals effectively. The impact of noise, the length of a signal frame, the number of sources and the number of observed mixtures on the performance is investigated in detail It is also shown that regarding a noise as an independent source is not always correct.     

Signal Level Simulation Modeling for Antenna Array of Aperture Synthesis Radiometer Based on the Equivalent Complex Baseband Representations

This paper presents a signal-level simulation model for simulating the process that antenna array of Aperture Synthesis Radiometer (ASR) collecting thermal radiation and transforming thermal radiation signal into radio frequency (RF) signal. By using the equivalent complex baseband signals to represent the practical thermal radiation and RF signals, simulation efficiency is improved significantly. The statistic characteristics of simulation results are found to match the corresponding theoretical analysis well. Results of an imaging simulation experiment show that this model can be employed in ASR system-level simulator design.