离轴位相奇点的动态传输

推导出高斯背景的离轴位相奇点光束的半屏衍射解析公式,详细研究了离轴位相奇点的动态传输.结果表明,半屏衍射,偏移量和传输距离都会影响位相奇点的传输行为和衍射场位相奇点的分布.改变偏移量和传输距离,衍射场伴随有位相奇点的产生,移动和湮没. 关键词： 奇点光学 离轴位相奇点光束 半屏衍射 光涡漩     

附加克尔介质Jaynes—Cummings模型场的位相特性

运用Pegg-Barnett厄米位相公式,研究了附加克尔(Kerr)介质Jaynes-Cummings(J-C)模型场的位相特性.具体讨论了场的位相概率分布、厄米位相算符的期待值以及位相的涨落,通过与标准J-C模型作比较,讨论了克尔介质与模场的非线性相互作用对场位相特性的影响.     

基于位相抽取的三维信息加密算法研究

本文提出了以位相抽取为基础的三维信息加密算法.构造由纯振幅和纯位相物体组成的简单三维信息作为加密对象.先用标量衍射理论计算其复振幅并抽取相位分布,再结合双随机位相编码完成加密.解密算法为上述算法的逆过程.计算机模拟结果证实了该算法的有效性、鲁棒性和安全性,并揭示了位相抽取算法用于加密更大信息量三维信息的潜力. 关键词： 傅里叶光学 光学信息安全 三维信息加密 位相抽取     

一种新的奇偶非线性相干态的位相统计性质

根据Pegg-Barnett位相定义, 计算了一种新的奇偶非线性相干态的位相概率分布函数, 利用数值计算方法研究了它们的位相统计性质. 数值计算结果表明：新的奇偶非线性相干态的位相特性与通常奇偶相干态的位相特性截然不同.     

三环位相型光瞳滤波器的横向超分辨与轴向焦深扩展

用矢量衍射方法分析了线偏振光入射到带有三环位相型光瞳滤波器的高数值孔径物镜时,焦点的轴向和横向光强分布.数值模拟结果表明,高数值孔径物镜聚焦时需同时考虑光强的轴向和横向分布.通过加入三环位相光瞳滤波器,在实现横向超分辨的同时实现了光学系统轴向焦深扩展和轴向光强分布平坦化,并且位相调制深度变化时,会出现轴向焦移现象.对三环位相光瞳滤波器结构进行了优化,得出了优化结果. 关键词： 光学超分辨 扩展焦深 位相型光瞳滤波器 矢量衍射方法     

Roy-型奇偶非线性相干态的位相概率分布

借助于数值计算方法，研究了Roy-型奇偶非线性相干态的位相概率分布特性.结果表明，它们的位相概率分布不同；与通常的奇偶相干态不同，在这种新的奇偶非线性相干态中，Pegg-Barnett位相概率分布能明显地反映出不同的量子干涉特性. 关键词： Roy-型奇偶非线性相干态 Pegg-Barnett位相算符公式 位相概率分布     

零相关位相板准远场应用的数值研究

对零相关位相板匀滑准远场散斑的特性进行了数值模拟,并与使用随机位相板(配合二单元 偏振控制板)的情形进行了比较.结果表明,尽管零相关位相板是针对入射场为平面波和作为 远场应用而设计的,但在准远场应用中,当离焦距离不超过0002355λf²/d2,入射场的振幅随机起伏不超过10%和位相随机起伏不超过λ/2０的情况下,其 散斑的光强起伏仍明显低于采用随机位相板的情形.因而,零相关位相板在准远场应用中仍 能有效地匀滑散斑. 关键词： 零相关位相板 准远场散斑匀滑 激光聚变     

一种二元整形元件激光直写方法的实验研究

为了实现具有复杂位相结构的二元光束整形元件,提出了采用方光点的激光直写系统来逐点光刻浮雕位相结构的方法,通过双远心投影缩微光路获得5-20 μm方点,光点尺寸对应于最小位相单元,从而获得了位相结构的高质量直写.分析了高斯光点和方光点位相单元结构对二元整形元件衍射效率的影响,方形两台阶二元整形元件的+1级衍射效率达到31%,给出了实验结果.     

相量的q形变相干态及其压缩性质

研究位相正交算符在相量的q形变相干态中的压缩性质和二能级系统中粒子数-位相压缩及其不确定关系，进而得到了一些新的粒子数-位相不确定态. 关键词：     

彩色全息显示中液晶空间光调制器位相调制偏差的矫正方法

采用三基色激光照明并结合时分复用或空间复用技术,可实现基于液晶空间光调制器(LC-SLM)的彩色全息显示.但由于在不同激光波长入射条件下LC-SLM的位相调制特性曲线不同,难以同时满足多波长入射条件下2π线性位相调制的要求,致使彩色全息再现结果受到共轭像和零级斑的干扰.针对该问题,本文通过实验测试获得LC-SLM在不同波长入射时的位相调制特性曲线,并分析了RGB激光器各分量的位相调制特性曲线非线性偏差和调制幅度偏差对多阶位相型傅里叶变换相息图再现效果的影响.根据"查表法"建立了各波长入射条件下满足2π线性位相调制的灰度映射关系,并对RGB分量相息图进行修正.通过对修正前后RGB分量相息图的数值模拟再现和光电再现实验与分析,结果表明:该方法有效地克服了LC-SLM位相调制特性曲线偏差的不利影响,从而改善了彩色全息显示中各分量相息图的再现质量.     

Effects of bond alternation and the Dzyaloshinskii-Moriya interaction on the ground-state phase diagram of the Ising model

The bond-alternative ferromagnetic Ising model with the Dzyaloshinskii-Moriya (DM) interaction is investigated using an infinite time-evolving block decimation (iTEBD) algorithm, and two interesting phase diagrams are proposed. Without bond alternation, there are only two well-known phases (a ferromagnetic phase and an x-y spiral (chiral Luttinger liquid) phase). Once the bond alternation is taken into account, two additional interesting phases (a z-chiral and a z-stripe phases) are induced. Nonzero chiral order is observed in all phases except the ferromagnetic phase. Two kinds of chiral phase, with or without string order, are identified. With the y-axis DM interaction, the phase diagram becomes relatively simple, and consists of only two different phases (a ferromagnetic phase and a y-chiral phase). First-order metamagnetic phase transitions from the ferromagnetic phase into the other phases are observed in both cases.     

Phase transformations during the growth of paracetamol crystals from the vapor phase

Phase transformations during the growth of paracetamol crystals from the vapor phase are studied by differential scanning calorimetry. It is found that the vapor-crystal phase transition is actually a superposition of two phase transitions: a first-order phase transition with variable density and a second-order phase transition with variable ordering. The latter, being a diffuse phase transition, results in the formation of a new, “pretransition,” phase irreversibly spent in the course of the transition, which ends in the appearance of orthorhombic crystals. X-ray diffraction data and micrograph are presented.     

Studying the current-voltage characteristics of liquid-crystal langmuir films in the region of the ferroelectric phase transition

The electrophysical properties of hyperfine films of liquid crystals are studied. At temperatures near the phase transition, singularities in the curves of the temperature dependence of the sample capacitance are found. Hypotheses regarding the nature of the phase transition are proposed. A change in the electrical conductivity of the samples based on a TDOB AM BCC liquid crystal is detected upon the ferroelectric phase transition. Hypotheses regarding the causes of the influence of the phase transition on the electrophysical properties of the films are put forward.     

Macroscopic description of the ferromagnetic superconductors

We present an improved analysis of the phase transitions in spin-triplet ferromagnetic superconductors within Ginzburg–Landau theory. We put special emphasis on the phase transitions from normal phase to the mixed phase of coexistence of ferromagnetism and unconventional superconductivity. We present a detailed analysis of the different phases that can occur and analyze the question under which conditions the phase transitions from normal phase to the mixed phase of coexistence of ferromagnetism and unconventional superconductivity are possible when compared to other phase transitions. The conditions for the phase transitions and the stability conditions are calculated. On the basis of this model, it is argued that the transition from normal phase to the mixed phase of coexistence is always of first order. It was observed from the theoretical calculations that the transition from the ferromagnetic phase to the coexistence phase can cross over from the first to the second order at the tricritical point.     

On the nature of the phase transitions in cadmium pyroniobate

The existing, doubtful interpretations of the numerous phase transitions in cadmium pyroniobate Cd₂Nb₂O₇, which is a ferroelectric with a pyrochlore-type structure and a Curie temperature lying near 200 K, are critically analyzed. The manifestations of all phase transitions in cadmium pyroniobate, the mechanisms proposed for these transitions, and doubts about their validity are discussed. Various dielectric anomalies observed near 200 K are related to three phase transitions in this temperature range. The causes of the large number of phase transitions observed in this material, the dislocation structure of the crystal, the diffuseness of the ferroelectric phase transition, and the relaxor properties of the crystal are also explained.     

在Jaynes－Cummings模型中压缩真空初态场位相演化特性

应用Ｐｅｇｇ－Ｂａｒｎｅｔｔ位相理论，研究了Ｊａｙｎｅｓ－Ｃｕｍｍｉｎｇｓ模型（Ｊ－Ｃ模型）中压缩真空初态场位相演化特性，具体计算了弱压缩条件下，场的位相几率分布函数及位相涨落，给出了在极坐标中位相几率分布演化曲线，讨论了原子与场相互作用对场的位相性质的影响。     

Reexamining the phase diagram of the Gay—Berne fluid

This work reexamines and updates earlier investigations on the phase behaviour of the Gay-Berne liquid crystal model, concentrating on the effect of varying temperature. Constant volume and constant pressure Monte Carlo simulations are combined for systems consisting of N = 500 molecules along different isotherms over the reduced temperature range 0.60 ≤ T ≤ 1.25. As in previous simulation studies of the model, the study identifies nematic and smectic B phases on compressing the isotropic fluid, the particular phase sequence depending on temperature. The nematic phase is found to be stable with respect to the isotropic phase for reduced temperatures T ≥ 0.75. In the temperature range 0.75 ≤ T ≤ 1.25, the phase boundaries of the isotropic-nematic transition are obtained by computing the Helmholtz free energy of both phases from thermodynamic integration. From the simulation data, the relative volume change at the isotropic-nematic transition is about 2%, and this value appears to be rather insensitive to changes in temperature. On compressing the nematic phase, the Gay-Berne fluid undergoes a strong first-order transition to the smectic B phase. This transition is studied by using constant pressure simulation, and the coexistence properties are estimated from the limits of mechanical stability of the nematic phase. Larger relative volume changes are found at the transition than those suggested by previous studies, with typical values increasing up to 10.5% as the temperature is decreased. The results are consistent with the existence of strong coupling between nematic and smectic order parameters. For temperatures T ≤ 0.70 the nematic phase is no longer stable, and the phase sequence isotropic-smectic B is observed. Therefore, the Gay-Berne model exhibits an isotropic-nematic-smectic B triple point. Extrapolating the present simulation data, this triple point is located approximately at reduced temperature T_INB ? 0.70 and reduced pressure P_INB ? 1.825.     

弱散射体产生的菲涅耳极深区散斑场相位涡旋演化的实验研究

实验提取了弱散射体产生的菲涅耳极深区的散斑场.发现当散射距离一定时,弱散射体光场的相位分布特征随散射体的粗糙度的变化而变化;对于某一弱散射体,相位分布特征随散射距离的变化而变化;当弱散射体的粗糙度大到一定程度时,才产生相位涡旋现象;散射体表面上存在相位涡旋;弱散射体产生的相位涡旋的密度随散射屏粗糙度的增大而增大,还随散射距离的增大而增大.研究结果对于认识弱散射体的相位及相位涡旋分布特征随粗糙度和散射距离的演化具有重要意义,而且对于认识散斑场随散射距离的演化有一定的帮助.     

激发压缩真空态的相位概率分布

应用Pegg和Barnett提出的相位算符和相位态理论,研究了激发压缩真空态的相位概率分布特性.数值计算结果表明,激发压缩真空态的相位概率分布主要受到相位参量和压缩参量的调节,相位参量使相位概率分布呈峰值结构,压缩参量的变化将影响相位概率分布的峰值强度,此外激发光子数对相位概率分布也有较大的影响.