基于Fibonacci序列准周期结构的小角度低通空间滤波器

利用常规材料构造了Fibonacci序列准周期结构,运用传输矩阵法研究了该结构的空间传输特性,并基于该结构优良的空间传输特性设计了小角度低通空间滤波器.数值模拟结果表明,该小角度空间滤波器的角域带宽可通过改变序列的结构类型和序列数来调谐,其调谐规律为:随着Fibonacci序列F(m,1)中m值的增加,对应空间滤波器的角域带宽减小;随着序列数的增大,对应角域带宽也减小.在调谐的基础上,还可通过改变构成准周期结构的介质折射率参量来精确调节其角域带宽.相比于基于超材料的小角度空间滤波器而言,基于Fibonacci序列的小角度空间滤波器制备更简单,且有望应用于新一代的高功率激光系统中.     

平面圆形膜片式光纤布拉格光栅温度补偿压强传感

报道了利用光纤布拉格光栅反射波谱带宽展宽技术实现温度补偿的压强传感新方案。结合平面圆形膜片应变调谐的特点,采用膜盒式结构,将光纤光栅中心对准平面圆形膜片零应变半径并沿径向粘贴,利用反射波谱带宽对应变敏感而对温度不敏感的特性解调压强,成功地实现了温度补偿的压强传感测量。基于光谱分析仪0.05nm的光谱分辨力,实验测得带宽随压强响应灵敏度为0.34nm/MPa,压强精度为±0.15MPa,压强测量范围为0~7.5MPa。实验结果与理论分析基本一致。     

LED照明的光栅光调制器光学特性分析与实验

针对一种新型的光凋制器--光栅光调制器,研究用LED作为其照明光源时对光学调制特性的影响.以部分相干光理论为依据,结合MATLAB仿真,推导出用LED照明光栅光调制器时,光源带宽对成像对比度具有较大的影响,通过滤色片将光源带宽减小到13 nm时,像面上的对比度约为150,进一步减小带宽至10 nm,对比度将达到225.光源的尺寸在与光源到光栅光调制器之间的距离相比小于0.03时,对光栅光调制器的光学信息处理不会有影响,并通过实验加以证实,从而说明采用LED作为光栅光调制器照明光源的可行性.     

Numerical studies of atomic three-step photoionization processes with non-monochromatic laser fields

The atomic selective multi-step photoionization process is a critical step in laser isotope separation. In this work, we study three-step photoionization processes with non-monochromatic laser fields theoretically based on the semi-classical theory. Firstly, three bandwidth models, including the chaotic field model, de-correlation model, and phase diffusion model, are introduced into the density matrix equations. The numerical results are compared with each other comprehensively. The phase diffusion model is selected for further simulations in terms of the correspondence degree to physical practice. Subsequently, numerical calculations are carried out to identify the influences of systematic parameters, including laser parameters (Rabi frequency, bandwidth, relative time delay, frequency detuning) and atomic Doppler broadening, on photoionization processes. In order to determine the optimal match among different systematic parameters, the ionization yield of resonant isotope, and selectivity factor are adopted as evaluation indexes to guide the design and optimization process. The results in this work can provide a rewarding reference for laser isotope separation.     

等离子体填充耦合腔链特性研究

 用严格的场匹配方法分析了填充等离子体的耦合腔链，研究了等离子体 腔混合模的形成以及“冷带宽”和“热带宽”的展宽效应。等离子体填充周期性耦合腔链后，形成周期性的截止频率为0的等离子体TG模式。当填充的等离子体密度较大，且腔模和TG模式发生部分重叠时，两者相互耦合，形成等离子体 腔混合模式。工作在混合模式下，其“冷带宽”和“热带宽”大大增宽，且耦合阻抗比真空时提高了近5倍，因此在填充等离子体后，耦合腔链的慢波特性得到了显著的改善。     

格兰泰勒棱镜高性能宽带减反射膜的优化设计及性能测试

格兰泰勒棱镜在光学领域有着重要的应用,透过比的高低和有效带宽的大小,直接影响着棱镜的品质.为了提高棱镜的透射率,拓宽有效使用带宽,借助于计算机辅助设计方法,设计了高性能多层减反射膜系:选用合适的光学薄膜材料,利用电子束蒸镀,借助于离子源辅助蒸镀,制作了高性能的宽带减反射膜.测试结果表明:平均剩余反射率小于0.5%,有效使用带宽在可见光区大于100 nm,达到了设计要求,提升了棱镜的品质.     

组合脉冲宽带去耦

本文在理论分析的基础上,提出了一新的用于异核宽带去耦的组合脉冲:90°(X)150°(Y)70°(-Y)150°(Y)90°(X)。理论和实验表明,由此组合脉冲组成的去耦序列:NEW-16、NEW-32,去耦谱宽比常用的去耦序列:MLEV-16、WALTZ-16的去耦谱宽增加约30%。本文还提出了一种电路,使现已提出的大多数组合脉冲去耦序列,能在Varian XL-200 NMB谱仪上实现。     

介绍一个验证光量子性的简易实验──内光效应

内光电效应是光的量子性的又一实验验证，本文介绍了其原理方法，方便可行，有推广价值。     

Metropolitan Optical Networks: When to Change to DWDM

In this article we propose a new methodology to estimate the change in the bandwidth demand in time, mainly in residential areas. The bandwidth demand forecast is a basic aspect to decide the evolution of metropolitan optical networks. The word evolution refers to the necessity of making changes in networks, either by upgrading or replacing different elements that are part of the network. This analysis, along with a technological alternatives analysis, provides the operator the needed information to achieve the appropriate network planning and to make investment decisions.     

Admission control of multi-class traffic with service priorities in high-speed networks

We consider a fluid model of a system that handles multiple classes of traffic. The delay and cell-loss requirements of the different classes of traffic are generally widely different and are achieved by assigning different buffers for different classes, and serving them in a strict priority order. We use results from the effective bandwidth of the output processes (see Chang and Thomas (1995)) to derive simple and asymptotically exact call-admission policies for such a system to guarantee the cell-loss requirements for the different classes assuming that each source produces a single class traffic. We compare the admission-control policies developed here with the approximate policy studied by Elwalid and Mitra (1995) for the case of two-class traffic. This revised version was published online in June 2006 with corrections to the Cover Date.