纳米晶体线的晶格动力学格林函数及晶格振动

通过求解差分方程,推导了纳米晶体线的晶格动力学格林函数,分析了其晶格振动,并推导了声子数表象中的原子位移及晶格振动哈密顿公式.研究结果表明,纳米晶体线的晶格振动能带分裂为一系列的子带,格波只能沿纳米晶体线的纵向传播,沿纳米晶体线的横截面只存在驻波.     

通过光子与横向光频支声子直接耦合产生超声

详细地讨论了通过光子与横向光频支（TO）声子直接耦合产生高频超声问题。着重研究如下的原则性的实验方案：在构成共振腔主体的离子晶体中掺入某种活化原子（犹如固体激光器中受到抽运的杂质原子）,其受激辐射的光能用于激发TO声子,从而获得超声振动向腔外的输出。分析的结果说明,为保证运行的稳定性,体现在声子与光子的非线性耦会以及声子间耦合的晶格振动非简谐性是必要的。对这种光一声装置的工作物质的探索,将关系到对离子晶体晶格动力学上的非线性及有关电磁耦合特性的深入研究     

压电体超晶格中的新型极化激元

对压电体超晶格中电磁波的传播情况进行了研究，通过压电效应，压电体超晶格中的纵振动声波将引起横向电极化，这一极化会与某一特定波段的电磁波强烈耦合，从而出现通常离子晶体中所没有的新型极化激元，产生非布拉格反射引起的光学禁带。     

黄昆对物理学的贡献

黄昆是晶格动力学的奠基人和权威,声子物理学科开拓者。他是多声子光跃迁和多声子无辐射跃迁理论学科的开创者,是“极化激元”概念的最早阐述者。他的姓氏也与晶格振动长波唯象方程、X光漫散射理论联系在一起。在多年离开科研第一线后,黄昆70岁还建立了半导体超晶格光学声子的“黄－朱模型”。本文简要介绍黄昆先生在科学研究领域的几项主要贡献。     

离子晶格非简谐振动引起的光学非线性与增强吸收型光双稳

处理了光场（电磁场）与离子晶体的非简谐性振动之间的相互作用问题。导出了用简正坐标即声子模式所表达的非线性晶格动力学和非线性宏观极化。在旋转波近似下，得到在入射光驱动下光子－声子耦合体系的总的相干性哈密顿算符。通过相应的静态方程证明该耦合系统会出现增强吸收型光学双稳性，这也就证明了光场与各种玻色子型固体元激发，如光频支声子和半导体中激子的非线性耦合可以作为增强吸收型光双稳的机制。     

KTiOPO4晶体的太赫兹光学声子振荡特性研究

采用超快半导体光电导开关的宽带太赫兹时域频谱系统,研究了 KTiOPO4 晶体在0.5～2.0THz波段的光学声子振荡特性;在晶体z轴平行于THz波电场振动方向时发现了明显的吸收峰.利用晶体中晶格振动模式（光学声子）对光谱的选择性吸收特性和多洛仑兹振子伪谐振介电模型,很好地拟合了KTP晶体的复介电常量曲线,得到了对应晶格弱振动的光学声子的频谱参量值.研究结果表明,位于ω1 /2π=1.76 THz的吸收峰是KTP晶体中沿z轴排列的K+相对于PO4和TiO6晶格振动造成的光学外振动模.同时也说明THz波对于晶格弱振动非常敏感,对于微弱的光学声子吸收峰的频谱分析更加精准.     

离子晶体非简谐振动引起的光学非线性与增强吸收型光双稳

处理了光场与离子晶体的非简谐性振动之间的相互作用问题。导出了用简正坐标即声子模式所表达的非线性晶格动力学和非线性宏观极化。在旋转波近似下，得到在入射光驱动下光子－声子耦合体系的总的相干性哈密顿算符。     

周期薄壁开口梁中的双耦合振动带隙

本文研究了由两种材料组合构成的周期性薄壁开口梁的弯曲和扭转双耦合振动。基于双耦合振动方程，给出了平面波展开法。当填充比不变时，晶格常数是影响带隙相对宽带的一个因素；当晶格常数和填充比不变时，杨氏模量是影响带隙宽带的主要因素，而不是密度。利用有限元法计算了有限周期结构的振动频率响应，在带隙频率范围内，振动衰减40dB左右。这些发现对于声子晶体的应用具有重要意义。     

声子气的状态方程和声子气运动的守恒方程

根据爱因斯坦的狭义相对论中质能的等效关系，把固体(本文指非导体)晶格(原子)的质量分为晶格(原子)的静质量和晶格热振动能量的等效质量两个部分，后者就是固体中声子气的等效质量.晶格(原子)热振动的能量则分为晶格(原子)静质量具有的热能以及声子气质量具有的热能.基于固体的状态方程，导得了晶格静质量热振动的状态方程和声子气的状态方程.声子气在固体介质中的宏观运动就是热量在固体中的传递过程.建立了声子气运动的守恒方程组，分析表明，忽略惯性力时声子气的动量守恒方程就退化为傅里叶导热定律，阐明了傅里叶导热定律的物理本质是声子气驱动力与阻力的平衡方程.当热流密度很大惯性力不能忽略时，傅里叶导热定律不再适用. 关键词： 非傅里叶导热 声子气 声子气质量 状态方程 守恒方程     

声子

前言 声子(phonon)是固体物理和近代声学中的一个重要基本概念.但一般固体物理、统计物理和声学的教科书或参考书中,对这一概念的介绍非常简单,甚至有一些不妥的说法,如认为“声子就是晶格振动中的简谐振子.”[1]为了使大家对声子有一个准确而完整的概念,本文拟就声子的引入、声子的性质进行较为详细的讨论.一、声子概念的引入 声子的概念首先是在研究晶格振动时引入的[2].晶格振动是晶体中诸原子(离子)集体在作微振动,其结果表现为晶格中的格波. 由量子力学可知,用经典力学的物理量来描述微观粒子,只能在一定的近似程度内做到.当作为粒子处…     

New type of polariton in a piezoelectric superlattice

We studied the propagation of an electromagnetic (EM) wave in a piezoelectric superlattice. Because of the piezoelectric effect, a transverse polarization can be induced by a longitudinal wave which couples strongly to the EM wave in some particular frequency regions, resulting in the creation of a new type of polariton that does not exist in ionic crystals. The forbidden band associated with the polariton is not due to the Bragg reflection, but rather to the coupling.     

Magnetoelectrically coupled polariton excitation in a plasmonic crystal composed of nanorod dimers

In this work, the long wavelength optical properties of a plasmonic crystal, composed of gold nanorod dimers arranged parallel, have been studied. Due to the strong coupling between incident light and the oscillation of free electrons inside nanorod dimers, the magnetically induced and/or magnetoelectrically coupled plasmonic polaritons can be excited. A theoretical demonstration has been proposed and coupled equations that show similar profiles to the Huang-Kun equations for ionic crystals have been deduced, indicating the constitutive abnormalities and polaritonic bandgap effect. The analogy between the magnetoelectrically coupled metamaterials and ionic crystals may shed light on physical explanations, as well as constitutive parameter retrieval, for the magnetoelectric metamaterials.     

基于光子晶体塔姆态的带隙分裂

将由两个一维介质层光子晶体组成的异质结拓展为超晶格结构,分析了该结构的能带和透射谱。该超晶格结构可以产生多个界面隧穿态,它们之间的耦合可产生新的通带。研究结果表明,该通带的宽度随光子晶体的周期数变化,而通带的中心位置保持不变。当光子晶体周期数取特定值时,这个通带将发生分裂,在带间产生零相位带隙或π相位带隙。     

Collective excitations in fast ion conductor superlattices

Within the framework of the electromagnetic theory, the collective modes in the superlattice system composed of superionic conductors and ionic crystals are studied. The superionic conductor is described by the hydrodynamical model in which the anion cage is immersed in the cation liquid. The behavior of the modes are analysed in terms of the coupling strength between excitations pertaining to different layers. The coupling strength is controlled by varying the slab thicknesses. An interesting behavior in which the diffusion mode transforms to the relaxation mode when the coupling strength is varied from strong to weak is obtained. Also, the effect of the coupling strength on the acoustical and optical modes are shown.     

Complete reorganization of the mode structure of the wave function of a channeled electron in a crystal with a superlattice

The dynamics of relativistic electrons subjected to planar channeling in distorted crystals is investigated using step-by-step numerical integration of the Schrödinger equation. It is shown that periodic distortion of a planar channel (the formation of a “superlattice”) can cause complete reorganization of the mode structure of the wave function. In the limit of weak perturbations of the crystal lattice, the simulation results are consistent with the analytical results from perturbation theory. The position of each line in the spontaneous emission spectrum in the case of resonant distortions depends on the length of the superlattice period.     

掺杂钾钠铌酸锶钡光折变晶体的各向异性衍射

本文给出了关于光折变晶体各向异性衍射的二波耦合方程,还给出了三种分别掺Cu,Ce,Co的钨青铜结构系列单晶(厚度为0.6—0.8cm)钾钠铌酸锶钡(KNSBN)在He-Ne激光(λ=6328?)照射下产生的光致光栅衍射实验结果。根据二波耦合理论,解释了这三种光析变晶体的衍射图样分布。根据波矢图的分析得出结论:对于不同性(正或负)单轴晶体,只能存在一种各向异性衍射的圆环图样(e→o衍射或o→e衍射)。理论分析与实验基本符合。 关键词：     

Flexomagnetoelectric interaction in cubic,tetragonal and orthorhombic crystals

The phenomenological theory of the flexomagnetoelectric coupling in crystals of the cubic, tetragonal and orthorhombic crystal systems has been suggested. Secondary role of the crystal structure chirality was shown. Oppositely, significant role of the crystallographic point group type (symmetric, alternating, dihedral or cyclic) in the flexomagnetoelectric coupling has been derived. It was shown, that conceptually new features of the flexomagnetoelectric effects are expected in the crystals of the cyclic groups (crystal classes 4/m, 4? and 4). Proposed verification of the theory is investigation of the domain wall bend details (changes of the effect symmetry). Special case of such verification near the compensation point is suggested. First-principles mechanisms of the flexomagnetoelectric interaction were discussed.     

稀土掺杂光学超晶格的自变频激光模型与应用

通过结合准相位匹配理论和空间分布自混频（或自倍频）激光模型提出了稀土掺杂光学超晶格材料自变频激光理论模型，该模型计入了弱聚焦的高斯光束空间分布，泵浦耦合以及非理想周期结构的影响，并应用该理论模型对Nd^3 离子掺杂非理想周期极化铌酸锂（Nd^3 :APLN)晶体同步自变频多波长激光进行了模拟计算，计算结果，尤其是阈值、可见激光总输出功率和同步可见激光谱线相对强度分布等与实验结果符合得很好，从而表明该模型的有效性。     

Solitons in two-and three-dimensional crystals at Fermi resonance of optical modes

It is shown that soliton excitations of the peak, crater, and dark types, previously found by authors only in one-dimensional crystals, exist in two-and three-dimensional crystal systems of the superlattice type at Fermi resonance of modes of adjoining crystals. An analytical solution for the central part of soliton envelopes is presented. A numerical calculation gives results coinciding with the analytical solution in the central part of the solitons and demonstrates the presence of oscillations of the envelopes on the wings of peak and crater solitons in two-and three-dimensional crystals, which are not observed in one-dimensional crystals. Fiz. Tverd. Tela (St. Petersburg) 41, 712–716 (April 1999)