可调谐激光器腔内色散棱镜及其组合

分析了色散棱镜的特性及其顶角设计问题。讨论了色散棱镜和扩束棱镜在布鲁斯特角入射状态下，可组合使用的形式及单程角色散。提出将色散棱镜与扩束棱镜组合使用，可减少色散棱镜个数而获得更大角色散的方法。并据此设计了两个色散棱镜组，在Ｔｉ∶Ｓ激光器中得到实际使用。     

棱镜色散成像光谱仪的谱线漂移特性

为了研究棱镜色散成像光谱仪的谱线漂移特性,介绍了成像光谱仪谱线漂移的影响因素及机理,基于线性光学模型建立了描述谱线漂移特性的数学模型.在Matlab环境下利用Code V的API函数对系统进行了光线追迹,验证了数学模型的正确性,分析了谱线漂移的灵敏度系数.结果表明:工作环境变化引起的镜面刚体位移是导致成像光谱仪谱线漂移...     

基于Offner中继结构的机载棱镜色散成像光谱仪系统设计

考虑到机载遥感平台对成像光谱仪小型化、轻量化要求的逐渐提高,在分析了主要几种成像光谱仪特点的基础上,重点阐述了技术成熟度较高的光栅色散和棱镜色散型成像光谱仪,研究了基于Offner中继成像结构的紧凑型成像光谱系统。结合Offner同心光学系统成像特点,在给定系统指标的情况下,设计出了两种在发散和会聚光束中使用色散元件的全球面光谱系统,给出了系统的调制传递函数、点列图以及系统谱线弯曲、色畸变曲线。结果表明,两种结构的Offner成像光谱仪,实现了遥感仪器小型化的目的,具有接近衍射极限的优良成像性质。同时,很好地控制了系统的谱线弯曲和色畸变,保证了获取光谱数据的一致性。     

变折射率组合三角棱镜产生无衍射线结构光

提出一种可产生大焦深无衍射线结构光的新型光学元件——变折射率组合三角棱镜,由正、负等腰三角棱镜胶合在一起设计而成,其变换光束特性与单个正等腰三角棱镜相同,等效折射率由正、负等腰三角棱镜折射率之差决定,因此可通过两个折射率接近的正、负等腰三角棱镜组合得到一个更加接近1的等效折射率,以获得更大焦深的无衍射线结构光,解决了单个正等腰三角棱镜小角度加工困难的技术问题。采用几何光学理论分析了产生无衍射线结构光的原理,计算了无衍射线结构光的相关参数。由衍射积分理论分析和模拟了新型光学元件后的光强分布特性。研究表明,平面波正面入射新型光学元件可以产生具有大焦深的无衍射线结构光。     

棱镜光谱线弯曲的分析

分析了三棱镜光谱线弯曲的原因和弯曲的方向。     

测量棱镜色散规律的方法改进

对目前实验教科书中研究棱镜色散规律常用的方法具有数据多、用时长及技巧性强的不足,提出了一种比较简洁直观的测量棱镜折射率的方法,即直接测量光线的入射角和不同频率光的出射角,用折射定律即可算得各色光的折射率.通过与传统的实验方法相比较,结果表明在准确度上二者是一致的.最后用Matlab拟合出棱镜的色散曲线及公式.     

新型棱镜产生近似无衍射线结构光

为了改善三角棱镜系统产生近似无衍射线结构光的能量均匀分布在若干条光斑上,不适合直接应用于三维表面测量且中心光斑对能量利用率较低的问题,提出了一种新型光学元件.该元件在三角棱镜的基础上,通过在其底部胶合一个与原三角棱镜底面大小相等,横截面为等腰梯形的凸台制成.采用几何光学的理论对新型光学元件的光束变换特性进行分析,结果表明其可以等效为两个不同底角三角棱镜的组合,平面光束通过新型光学元件后将产生中心光斑较强的近似无衍射线结构光.由衍射积分理论分析和模拟了新型光学元件后的空间光强分布特性.仿真的结果表明,衍射积分分析的结果与几何光学分析的结果是一致的:新型光学元件可以产生一种性能更好的近似无衍射线结构光.并且通过改变棱镜的结构参量,能够方便地调节光束的中心光斑尺寸、近似无衍射范围等参量.     

双棱镜干涉实验的研究

双棱镜干涉实验的快速调节与误差分析     

渥拉斯顿棱镜在不同方式组合下的光路特性分析

分析了具有相同结构角的两个渥拉斯顿棱镜在不同方式组合下的光路特性。给出了分束角与结构角的关系表达式,同时也给出了分束角与结构角的关系曲线。使用He Ne激光器(波长λ=633nm)对两个结构角S=27°的渥拉斯顿棱镜在四种不同组合方式下的光路进行了测试。结果表明,测试结果与理论计算完全相符。     

声表面横波压力传感器的电极质量负载效应分析方法

针对声表面横波(Surface Transverse Wave,STW)压力传感器,提出了一种考虑叉指电极质量负载的有限元和微扰理论结合分析方法。首先构建包含叉指电极的有限元模型,通过计算电极表面的面电荷得到器件的等效输入导纳,由导纳谐振点处提取STW传播声场,然后根据微扰理论,由STW传播声场以及压力引起的传感器结构的应力应变,得到包含电极质量负载影响的STW传感器的灵敏度。以一种基于ST-90°X石英材料的点压式STW压力传感器为例进行了理论计算,电极厚度为0.17 μm和0.21 μm时,计算灵敏度分别为-54.9 kHz/bar和-21.7 kHz/bar,说明电极质量负载对于传感器有较大影响。制作电极厚度为0.17 μm的传感器进行测试,得到-57 kHz/bar的压力灵敏度,实验结果和理论结果吻合,证明计算方法的有效性。     

大型轻质反射镜加工支撑状态的有限元分析研究

根据大型轻质镜加工过程中的受力情况 ,用有限元对镜子进行静力学分析和计算。分别计算了镜子的自重、磨盘正压力、磨盘剪切力等对镜面变形的影响情况。根据镜面变形规律设计了一系列支撑结构 ,最终确定了符合面形质量要求的支撑结构。     

二氧化碳探测仪典型透镜支撑结构的设计及分析

为了降低外界载荷和温度变化对二氧化碳探测仪光学系统透镜面形及共轴的影响,根据系统的特点和技术要求,对其典型透镜的支撑结构进行了研究,设计了一种径向挠性支撑结构并建立了3D实体模型。运用工程CAD分析软件,采用非线性有限元分析方法对其进行了动静刚度特性和热特性仿真分析,验证了支撑结构设计的合理性。分析结果表明,透镜结构组件的一阶固有频率为1 301 Hz;利用面型拟合,得到了各工况下镜面面形误差值为PV≤λ/10,RMS≤λ/50,偏转误差≤1″。该径向支撑结构能很好地保持透镜共轴精度,减小了温度变化对镜面变形的影响,各项结果满足设计要求,证明了结构设计的合理性。     

二氧化碳探测仪典型透镜支撑结构的设计及分析(英文)

为了降低外界载荷和温度变化对二氧化碳探测仪光学系统透镜面形及共轴的影响,根据系统的特点和技术要求,对其典型透镜的支撑结构进行了研究,设计了一种径向挠性支撑结构并建立了3D实体模型。运用工程CAD分析软件,采用非线性有限元分析方法对其进行了动静刚度特性和热特性仿真分析,验证了支撑结构设计的合理性。分析结果表明,透镜结构组件的一阶固有频率为1 301 Hz;利用面型拟合,得到了各工况下镜面面形误差值为PV≤λ/10,RMS≤λ/50,偏转误差≤1″。该径向支撑结构能很好地保持透镜共轴精度,减小了温度变化对镜面变形的影响,各项结果满足设计要求,证明了结构设计的合理性。     

金属线胀系数实验误差补偿的新方法——人工神经网络法

分析光杠杆法测量金属线胀系数实验的误差及误差产生原因,发现温度变化与刻度间隔并非线性变化.对比传统误差分析方法,利用神经网络非线性映射能力,对实验数据进行误差补偿分析,均方根误差达到0.000 01,消除非线性影响,误差降低.     

Determination of the structure factor for the rare gas fluids based on the ORPA theory and LIR equation of state

Linear isotherm regularity is applied to generate an expression for the direct correlation function (DCF), based on the optimized random-phase approximation theory. We use the Lennard-Jones potential in the modelling of real fluids, in which its molecular parameters are state-dependent. Based on the perturbation theory, we assume that the core contribution of the DCF is related to the geometric effect via a linear form, which arises from the excluded volume, and the tail contribution is related to the long-range intermolecular interactions of the system via a non-linear form. We use this model to predict the behaviour of the structure factor, S(k), in a wide range of k values for the xenon and krypton liquids. Finally, we compare our results with the experimental and theoretical data available in literature. The model is also successful in the presentation of the Ornstein–Zernike behaviour of S(k) at the low-k region.     

LEED crystallographic analysis for the structure formed by 2 ML of O at the Zr(0001) surface

A tensor LEED analysis is reported for the Zr(0001)-(1 × 1)-O surface which involves oxygen at a total coverage of 2 monolayers. The structure is indicated to have two layers of O: one forms an overlayer in which the O atoms bond to hollow sites of three-fold coordination on the regular metal surface, while the other layer has the O atoms in tetrahedral hole sites between the first and second metal layers. The stacking sequence, designated as (C)B(A)AB... corresponds to the first three layers of anion-terminated cubic ZrO₂, although some lateral compression is needed for superposition on the regular hcp Zr structure. The absorption of O in the tetrahedral holes results in a significant expansion in the first-to-second Zr---Zr interlayer spacing to about 3.44 Å from the bulk vaue of 2.57 Å. The O---Zr bond lengths are estimated to equal 2.07 Å for the overlayer O atoms, and 2.21 Å for the O atoms in tetrahedral hole sites. Comparisons are made with the structures of the corresponding 0.5 and 1 ML surfaces formed by the O/Zr(0001) system.     

Analytic Approximations for the Velocity of Field-Driven Ising Interfaces

We present analytic approximations for the field, temperature, and orientation dependences of the interface velocity in a two-dimensional kinetic Ising model in a nonzero field. The model, which has nonconserved order parameter, is useful for ferromagnets, ferroelectrics, and other systems undergoing order–disorder phase transformations driven by a bulk free-energy difference. The solid-on-solid (SOS) approximation for the microscopic surface structure is used to estimate mean spin-class populations, from which the mean interface velocity can be obtained for any specific single-spin-flip dynamic. This linear-response approximation remains accurate for higher temperatures than the single-step and polynuclear growth models, while it reduces to these in the appropriate low-temperature limits. The equilibrium SOS approximation is generalized by mean-field arguments to obtain field-dependent spin-class populations for moving interfaces, and thereby a nonlinear-response approximation for the velocity. The analytic results for the interface velocity and the spin-class populations are compared with Monte Carlo simulations. Excellent agreement is found in a wide range of field, temperature, and interface orientation.     

Band structure of surface states and resonances for clean Cu(1 1 0) surface

We have used the layer KKR method to calculate the Shockley and Rydberg surface states and resonances for Cu(1 1 0) for a given model of the surface potentials. This method has not been used before to predict all of the surface band structure for the energy range from the bottom of the conduction band to ∼7 eV above the vacuum level. The previous methods that used only local electron interactions in ab initio calculations could not produce the Rydberg surface barrier bands while those relying on nearly-free-electron parameterisation of bands could not deal with d-bands.     

Phase shift analysis and extraction of structure functions for Coulomb distortion on (e, e'p) reactions at high electron energies

New results for the double beta decay of ⁷⁶ Ge are presented. They are extracted from data obtained with the HEIDELBERG-MOSCOW experiment, which operates five enriched ⁷⁶ Ge detectors in an extreme low-level environment in the Gran Sasso underground laboratory. The two-neutrino-accompanied double beta decay is evaluated for the first time for all five detectors with a statistical significance of 47.7 kg y resulting in a half-life of T _1/2 ^2ν = [1.55±0.01(stat)^+0.19 _-0.15(syst)]×10²¹ y. The lower limit on the half-life of the 0νββ decay obtained with pulse shape analysis is T _1/2 ^0ν > 1.9×10²⁵(3.1×10²⁵) y with 90% C.L. (68% C.L.) (with 35.5 kg y). This results in an upper limit of the effective Majorana-neutrino mass of 0.35 eV (0.27 eV) using the matrix elements of A. Staudt et al.'s work (Europhys. Lett. 13, 31 (1990)). This is the most stringent limit at present from double beta decay. No evidence for a majoron-emitting decay mode is observed. Received: 22 August 2001 / Accepted: 18 October 2001