直接扣除法测量半导体光放大器频率响应

在光电子器件散射参量定义的基础上建立了基于直接扣除法的半导体光放大器频率响应测量系统,测量中通过扣除激光器和探测器系统的频率响应,得到放大器固有的频率响应。对InGaAsP体材料行波腔半导体光放大器样品进行了测量,得到了放大器在不同注入光功率和不同偏置电流下的频率响应曲线。这些曲线很好地反应了半导体光放大器的增益饱和和噪声特性,进一步分析发现半导体光放大器对低频调制信号的放大能力弱于对高频信号的放大能力,分析认为其原因在于半导体光放大器的载流子寿命有限导致低频信号长时间消耗载流子时,载流子数量无法及时恢复,从而使得增益降低。     

一种增益可调掺铒光纤放大器的研究

在所设计的增益可调掺铒光纤放大器中,采用可编程控制器PC机控制可变直流电压源引发压电陶瓷的电致伸缩效应,导致光纤布拉格光栅的Bragg波长发生漂移,实现被调制参数的变化.分析了双光纤光栅受到压电陶瓷电致伸缩效应时的反射谱变化规律和增益可调掺铒光纤放大器的放大特性.由该放大器的增益与输入信号功率的关系得出小的波长间隔,增益较小,但控制范围较大;大的波长间隔,增益较大,但控制范围较小的结论.在输入宽带光源时,得到两光纤布拉格光栅在不同中心波长之差时的掺铒光纤放大器的增益特性.     

宽量程微电流测量系统

宽量程微电流测量系统利用多增益前置放大器与可编程增益数据采集卡组成两级放大,通过PC机控制选择不同增益实现宽量程的测量,并对其噪声进行了仿真分析,提出了提高信噪比的措施.实验表明,该系统能对动态范围10-11~10-4A电流信号进行有效测量.     

基于光纤拉曼放大的级联式全光纤1020nm光源

设计并制作了输出功率为196 mW的级联式全光纤1020 nm光源.该光源采用光纤拉曼放大器与掺镜光纤放大器级联的放大方案,实现了对低功率1020 nm种子光的放大.在光纤拉曼放大级,采用了3段不同长度的拉曼增益光纤进行了对比实验,比较了一定信号光功率和抽运光功率下拉曼增益光纤长度对光纤拉曼放大级输出功率的影响;测量了...     

微弱光学图像的光参量放大特性的研究

研究了微弱光学图像在光参量图像放大中的放大特性,分析了相位匹配和晶体的空间频率带宽对图像信号增益的影响,从实验上验证了不同的相位匹配时输入图像信号在傅里叶平面上的增益分布.结果表明,当晶体的空间频率带宽大于输入图像信号的空间频率带宽且完全相位匹配时,光参量图像放大器能够对输入图像信号实现无失真、高增益的理想放大;有相位失配时,图像信号的增益峰值向高空间频率范围移动,并且在峰值附近范围变窄,随相位失配量大小的变化能够对图像信号光场中某特定空间频率实现放大,对图像信号进行滤波处理,突出图像特定频率的信息,实现图像边缘增强.     

F-P半导体激光放大器弱信号机制下的增益特性研究

利用直接耦合的激光器放大器对,观察了弱信号机制下Fabry-Perot的半导体激光放大器的光放大.测量了放大器增益随放大器注入电流的变化关系,并将实验结果同理论模型相比较,发现理论和实验是一致的.把F-P放大器看作是一个光电探测器,通过测量放大器的短路光电流,得到了激光器同放大器之间的耦合效率.     

1064nm波长双向泵浦的S波段掺铥石英光纤放大器

研究了1 064 nm波长双向泵浦的掺铥石英光纤放大器（TDSFA）,测量了信号开关增益随泵浦功率和信号波长的变化情况.在最大入纤功率1 400 mW泵浦下,放大器在1 485~1 517 nm的较宽范围内具有放大能力,最大增益3.76 dB.分析表明,弱的基态吸收和强的激发态吸收限制了放大器增益的进一步提高,表明上转换泵浦的TDSFA是可行的.     

一种可用于轨道角动量的受激布里渊放大的光子晶体光纤放大器

为了实现高纯度轨道角动量模式的传输和放大,本文提出了一种可用于轨道角动量的受激布里渊放大的光子晶体光纤放大器并对其结构进行了设计.利用有限元法在C波段内对该光子晶体光纤放大器的传输性能进行了系统分析,研究结果表明,该光子晶体光纤放大器可支持66种轨道角动量模式的高纯度传输和放大,其传输的轨道角动量模式的纯度均高于99.4%.通过对不同拓扑荷数的轨道角动量模式的布里渊增益谱进行系统的分析,发现均具有较高的布里渊增益系数(>7×10^-9 m/W),与现有的性能最优的OAM放大器相比提高了4—5个数量级,实现了较高的信号增益.该光子晶体光纤放大器的综合性能显著优于现有基于受激布里渊放大的光纤放大器和掺杂稀土离子的光纤放大器,这使其能够稳定、准确地对OAM模式进行同步放大和长距离传输,为轨道角动量模式激光系统的设计提供了一种可能.     

基于PIC及FPGA的简易信号分析仪设计

高速数据采集与信号分析是信号分析仪的关键。设计以PIC16F877A单片机为核心,DA芯片MCP4922及可变增益放大器AD603构成程控放大电路;CCP模块实现频率测量;AD转换器AD9288及FPGA实现高速实时数据采集,并由LCD液晶显示被测数据及波形。由单片机读取FPGA中FIFO的缓存数据,实现对正弦波、三角波、方波等幅值、电压真有效值的测量及信号波形判断,实验效果实用良好。     

微电流放大器在物理实验中的应用

为用集成运算放大器LM324制作的微电流放大器电路图．集成运算放大器是一种高电压增益、高输入电阻和低输出电阻的多级直接耦合放大电路，它不仅能够放大交流信号，而且能够放大缓慢变化的信号或直流信号．图1中ICI(1／4LM324)为信号放大部分，采用差动输入，外部输出调零．     

Chalcogenide Fibers: An Overview of Selected Applications

Chalcogenide glass fibers have many unique properties that make them attractive for applications that are not possible with silica fibers. Selected applications of chalcogenide fibers in research, commerce, and the military are reviewed.     

Some mathematical aspects of Anderson localization: boundary effect,multimodality, and bifurcation

Anderson localization is a famous wave phenomenon that describes the absence of diffusion of waves in a disordered medium. Here we generalize the landscape theory of Anderson localization to general elliptic operators and complex boundary conditions using a probabilistic approach, and further investigate some mathematical aspects of Anderson localization that are rarely discussed before. First, we observe that under the Neumann boundary condition, the low energy quantum states are localized on the boundary of the domain with high probability. We provide a detailed explanation of this phenomenon using the concept of extended subregions and obtain an analytical expression of this probability in the one-dimensional case. Second, we find that the quantum states may be localized in multiple different subregions with high probability in the one-dimensional case and we derive an explicit expression of this probability for various boundary conditions. Finally, we examine a bifurcation phenomenon of the localization subregion as the strength of disorder varies. The critical threshold of bifurcation is analytically computed based on a toy model and the dependence of the critical threshold on model parameters is analyzed.     

辣椒碱与β-环糊精包合物的核磁共振研究

利用核磁共振方法研究了辣椒碱β-环糊精包合物的化学计量比、空间结构信息及其在水溶液中的自扩散系数. 通过测定不同浓度比的辣椒碱和β-环糊精混合溶液的 ¹H NMR数据,绘制Job's曲线,辣椒碱和β-环糊精的Job's曲线均在r=0.5处出现拐点. 同时测定了该包合物的2D ROESY和DOSY谱图,ROESY谱图中NOE交叉信号出现在辣椒碱的H-1~H-8和β-环糊精的H-3′、H-5′、H-6′之间,DOSY测得β-环糊精和辣椒碱形成包合物前后的表观自扩散系数. 结果表明,辣椒碱β-环糊精包合物的主客体分子的化学计量比为1∶1,辣椒碱分子的异丙基端从β-环糊精的宽口端进入疏水腔,其中H-1~H-8部分在空腔内部,包合物的自扩散系数为2.95×10^-10m²/s.     

Darboux Transformation and N-soliton Solution for Extended Form of Modified Kadomtsev-Petviashvili Equation with Variable-Coefficient

The extended form of modified Kadomtsev-Petviashvili equation with variable-coefficient is investigated in the framework of Painlevé analysis. The Lax pairs are obtained by analysing two Painlevé branches of this equation. Starting with the Lax pair, the N-times Darboux transformation is constructed and the N-soliton solution formula is given, which contains 2n free parameters and two arbitrary functions. Furthermore, with different combinations of the parameters, several types of soliton solutions are calculated from the first order to the third order. The regularity conditions are discussed in order to avoid the singularity of the solutions. Moreover, we construct the generalized Darboux transformation matrix by considering a special limiting process and find a rational-type solution for this equation.     

The ρ-π Puzzle of J/φ and φ′ Decays

The recent BES Collaboration data on φ →PV, particularly the isospin violating mode φ′ → π^oω^o and finding of a finite number for B(φ′ → K^*OK^O), enable us now to deal more precisely about the challenges to theory concerning this extraordinary and remarkableso-called ρ-π puzzle of J/φ and φ′ decays. In terms of the existing data and deploying the simplest phenomenology, measurement of φ′ → π⁺π^- and whether a finite number for the K^*+K^- mode might require a significantly large accumulation of data remain interesting questions.     

Interaction of Wave Trains with Defects

The evolution and transition of planar wave trains propagating through defects(obstacles) in an excitable medium are studied. When the frequency of the planar wave trains is increased, three different dynamical regimes,namely fusion, "V" waves, and spiral waves, are observed in turn and the underlying mechanism is discussed. The dynamics is concerned with the shapes of the defects. Circle, triangle, and rectangle defects with different sizes are considered. The increase of pacing frequency broadens the fan-shaped broken region in the behind of a rectangle defect.The increase of width of a triangle defect leads to breakup of wave trains easier while the change of height shows opposite effect, which is presented in a phase diagram. Dynamical comparison on defects with different shapes indicates that the decrease of the defect width along the propagation of wave trains makes the fan-shaped region and the minimal frequency for breakup of spiral both increased.     

HL-2M 装置时序控制与数据采集系统设计

基于 FPGA 和 IEEE1588PTPv2 协议设计了 HL-2M 装置时序控制系统,用于在精准时刻为测控系统 提供触发。数据采集系统采用客户端/服务端双模式管理。在 HL-2M 装置初始等离子体放电实验中测试结果表明, 时序控制和采集系统具有纳秒级精度触发,实时性强,数据传输速度快,稳定可靠,方便部署和管理的特点,满 足 HL-2M 等离子体放电实验的应用需求。     

Double Diffractive Dissociation Process p + p(p) → Xp + Xp(p) + Π+ + Π- at High Energy and the Pomeron Model of Donnachie-Landshoff

Large p_γ charged pion pair produced in Double Diffractive Dissocjation (DDD) process at high energy is studied with double pomeron (IP) exchange mechanism. Using DonnachieLandshoff pomeron model we have calculated the cross-section of the process at the energy interval from ISR to LHC when the rapidity of the charged pions is approximately equal to zero. It is shown that this process is the favorite in experiments which could effectively be used to examine Donnachie-Landshoff pomeron model and provide a possibility to check the value of the suppression coefficient N².     

环位形下鱼骨模驱动快离子输运的数值模拟研究

考虑包含动理学效应的鱼骨模结构,使用导心轨道程序 ORBIT,在磁面坐标下研究了不同的扰动模 幅度、频率对快离子再分布的影响,并分析了粒子与扰动发生共振的条件。模拟得出,鱼骨模扰动会使快离子在 实空间、相空间中发生再分布,芯部( ψ_p/ψ _w≤0.2 ,ψ_p 为极向磁通,ψ_w 为最后一个闭合磁面的磁通)快离子密 度下降约 20%,中间磁面位置上( ψ_p/ψ _w≥0.2,ψ_p/ψ _w≤ 0.6)的快离子密度增加约 7%;通过扫描频率发现,相空间中快 离子的再分布对模式频率敏感,并分析了快离子与鱼骨模扰动共振的条件。     

CFETR N-NBI验证样机恒温供水系统的设计

通过分析中国聚变工程实验堆(CFETR)的基于负离子源的中性束注入系统(N-NBI)验证样机中等离子体电极的工况,确定了其恒温供水的技术参数,设计出了CFETR N-NBI验证样机恒温供水系统。