负折射率材料对产生Casimir排斥力的影响

研究了负折射率材料对产生Casimir排斥效应的影响. 两材料板间的Casimir排斥力的发生取决于两板以及其间媒质的电磁特性,通过理论与数值结果的分析研究给出电磁特性所影响排斥力的产生趋势. 对于由Drude-Lorentz型色散关系描述等效介电常数和磁导率的负折射率材料,调节各特征频率参数可实现Casimir排斥效应. 关键词： Casimir排斥力 负折射率材料 Drude-Lorentz型色散关系     

含负折射率介质非线性Bragg腔的双稳态特性

研究了含负折射率介质一维光子晶体非线性Bragg腔的透射特性、光学增强和双稳态特性.对负折射率介质无色散和有色散非线性Bragg腔及由两种正折射率介质构成的非线性Bragg腔的透射谱、光学增强、缺陷模的线宽、入射光的红移量、双稳态开关阈值进行了比较.含负折射率介质的非线性Bragg腔可显著增大腔内光学增强效应,降低缺陷模的线宽、入射光的红移量和双稳态开关阈值.     

色散磁导率对异向介质中的调制不稳定性的影响

基于Drude模型研究了异向介质的色散磁导率对调制不稳定性的影响. 结果表明，在反常色散情形，赝五阶非线性在异向介质的负折射区中增大了调制频谱的范围及增益值，这与常规正折射介质中出现的现象正好相反；自陡峭效应在异向介质中有可能为负值，但无论正负，也无论在正折射区还是负折射区，它都抑制调制不稳定性的产生；二阶非线性色散效应在正、负折射区中分别促进和抑制调制不稳定性的产生. 在正常色散情形，由于二阶非线性色散效应的作用，使本来在常规正折射介质中不可能出现的调制不稳定性现象也能出现，这一特性为在正常色散区形成孤     

含色散特异材料三明治结构的量子悬浮效应

在金属板与电介质材料板基底间插入色散特异材料板形成三明治结构,并对其Casimir作用力进行了研究.基于Casimir-Lifshitz理论,通过麦克斯韦应力张量计算了真空涨落的辐射压,并对三明治结构利用电磁模式传输矩阵方法进行了数值计算分析.计算结果表明,原本两板结构中存在的Casimir吸引力,在插入特异材料板后的三明治结构中将转变为斥力,从而使轻薄的金属板产生量子悬浮效应。讨论了特异材料板的色散电磁响应特性以及电介质板基底的影响,结果表明特异材料磁等离子频率越大、磁共振频率越小以及电介质板基底的介电常数越小时,三明治结构中获得的斥力越大.此外,板间距增加到一定范围时,三明治结构中将出现Casimir平衡回复力.特异材料填充因子越小、三明治结构中层距和层厚越大时,三明治结构间的回复力会出现在较长距的位置.三明治结构中的量子悬浮效应与平衡回复力可保证微纳米机械系统稳定性,展现出基于真空辐射压的应用前景.     

色散负折射特异介质的1维光子晶体缺陷态

在1维光子晶体中引入色散负折射特异介质,分析了其介电常数和磁导率在微波区（1～10 GHz）与频率的关系。分别对以色散负折射介质为缺陷的正折射率介质光子晶体及以正折射率介质为缺陷的正负折射率介质光子晶体进行了数值仿真,得出了均匀平面电磁波在正入射和斜入射时的透射谱。结果表明:在介电常数和磁导率均为负值的不同禁带中,分别出现了单、双缺陷模。利用透射谱的这一特点,可实现单、双通道滤波。     

磁电超材料折射率特性分析

基于麦克斯韦旋度方程, 将磁电超材料板中的电元件和磁元件分别等效为面电流和面磁流, 通过计算这些周期性面电流和面磁流在某个磁电超材料板上产生的总电场和总磁场, 获得了关于面磁流密度和面电流密度的两个方程, 进而推导出了周期性磁电超材料折射率与磁元件的磁导率、 电元件的介电常数和空间色散项之间关系的解析公式. 与传统的折射率计算公式不同, 该解析公式充分考虑到了空间色散以及磁电超材料的电元件和磁元件的相互作用. 折射率理论曲线和基于仿真实验数据的提取值曲线能很好地符合, 这说明文中推导的折射率公式能够正确地描述磁电超材料的负折射特性. 本文的结果将为分析电磁元件之间的相互作用以及设计负折射率符合一定要求的磁电超材料提供重要的理论参考. 关键词： 磁电超材料 周期性结构 负折射率     

正负折射率材料组成的一维光子晶体的能带及电场

计算了由正负折射率材料交替排列组成的一维光子晶体的能带及电场，发现其能带不同于由普通正折射率材料组成的光子晶体的能带.当选择合适的参数时，由正负折射率材料组成的光子晶体的TE模或TM模有完全光子带隙出现，这在普通光子晶体中不出现.导带中的电场波函数与普通光子晶体相比具有很强的局域性.对于负折射率材料层为色散介质的情况，计算了在不同的具有正负折射率区域能带.     

掺杂硅片与电磁超材料间的Casimir平衡恢复力

为探讨掺杂硅片与电磁超材料间的Casimir平衡恢复力的大小与相关材料参数间的变化关系,基于Lifshitz理论,采用格林函数得到麦克斯韦应力张量及单位面积Casimir力计算表达式,分析了掺杂硅片与电磁超材料板间的Casimir作用力.结果表明,掺杂硅片与电磁超材料板间Casimir作用力的大小和方向随着掺杂程度、材料厚度和填充比例因子的变化而改变,并能调控Casimir效应;且随着板间距的变化表现出平衡恢复力.     

色散磁导率对异向介质中的调制不稳定性的影响

基于Drude模型研究了异向介质的色散磁导率对调制不稳定性的影响. 结果表明,在反常色散情形,赝五阶非线性在异向介质的负折射区中增大了调制频谱的范围及增益值,这与常规正折射介质中出现的现象正好相反;自陡峭效应在异向介质中有可能为负值,但无论正负,也无论在正折射区还是负折射区,它都抑制调制不稳定性的产生;二阶非线性色散效应在正、负折射区中分别促进和抑制调制不稳定性的产生. 在正常色散情形,由于二阶非线性色散效应的作用,使本来在常规正折射介质中不可能出现的调制不稳定性现象也能出现,这一特性为在正常色散区形成孤 关键词： 异向介质 调制不稳定性 色散磁导率 二阶非线性色散     

掺杂硅片与电磁超材料间的Casimir平衡恢复力EI北大核心CSCD

为探讨掺杂硅片与电磁超材料间的Casimir平衡恢复力的大小与相关材料参数间的变化关系,基于Lifshitz理论,采用格林函数得到麦克斯韦应力张量及单位面积Casimir力计算表达式,分析了掺杂硅片与电磁超材料板间的Casimir作用力.结果表明,掺杂硅片与电磁超材料板间Casimir作用力的大小和方向随着掺杂程度、材料厚度和填充比例因子的变化而改变,并能调控Casimir效应;且随着板间距的变化表现出平衡恢复力.     

Repulsive and attractive Casimir forces between magnetodielectric slabs

The Casimir force between two parallel magnetodielectric slabs is investigated by means of Casimir–Lifshitz Theory. For two magnetodielectric slabs, one is permittivity-negative, while the other is permeability-negative in the real frequency space. Numerical results show that when the separation between these two slabs is small (or large), the Casimir force is repulsive, while for the intermediate separation, the Casimir force is attractive. As a consequence, there are two equilibria with zero Casimir force, and a repulsive–attractive–repulsive transition takes place with increasing the separation. Therefore, if the separation between two interacting slabs is manipulated in the small (or large) separation region, it is possible to overcome the stiction in micromechanical and nanomechanical systems.     

Tunable dual-band ferrite-based metamaterials with dual negative refractions

We report on three types of tunable dual-band metamaterial with dual negative refraction in this paper. The three types of metamaterial are composed of ferrite slabs and three different metallic resonators, including split-ring resonators (SRR), Ω-like resonators, and short wire pairs. The ferrite slabs under an applied magnetic bias provide one magnetic resonance frequency band and the three metallic resonators provide another magnetic resonance frequency band, respectively. The continuous wires within the metamaterials provide the negative permittivity in a wide frequency band covering the two magnetic resonance bands. We give the design, analysis and numerical demonstrations of three such types of metamaterial in detail. The effective electromagnetic parameters obtained from the simulated S-parameters indicate that the three types of metamaterial indeed exhibit two negative refraction passbands and the two passbands can also be shifted by changing the magnetic bias. Our results open the way to fabricate tunable dual-band metamaterial cloaks, absorbers, and antennas.     

Casimir force in presence of multi layer magnetodielectric slabs

By using the path-integral formalism, electromagnetic field in the presence of some linear, isotropic magnetodielectric slabs is quantized and related correlation functions are found. In the framework of path-integral techniques, Casimir force between two infinitely large, parallel and ideal conductors, with a different number of magnetodielectric slabs in between, is obtained by calculating the Green’s function corresponding to each geometry.     

Chiral Anomaly-Enhanced Casimir Interaction between Weyl Semimetals

We theoretically study the Casimir interaction between Weyl semimetals.When the distance a between semiinfinite Weyl semimetals is in the micrometer regime,the Casimir attraction can be enhanced by the chiral anomaly.The Casimir attraction depends sensitively on the relative orientations between the separations(b_1,b_2)of Weyl nodes in the Brillouin zone and show anisotropic behavior for the relative orientation of these separations(b_1,b_2) when they orient parallel to the interface.This anisotropy is quite larger than that in conventional birefringent materials.The Casimir force can be repulsive in the micrometer regime if the Weyl semimetal slabs are sufficiently thin and the direction of Weyl nodes separations(b_1,b_2) is perpendicular to the interface.The Casimir attraction between Weyl semimetal slabs decays slower than 1/a4 when the Weyl nodes separations b_1 and b_2 are both parallel to the interface.     

Repulsive Casimir force between gyroelectric slabs

We obtain the repulsive Casimir force between two parallel gyroelectric slabs, thus overcoming the difficulty that the repulsive Casimir force is difficult to achieve in a naturally occurring material. Under practically realizable parameters, we realize the crossover from attractive (repulsive) to repulsive (attractive) forces by changing either the external static magnetic field, the background permittivity of the gyroelectric medium, the slab’s thickness or the gap between the slabs. The proposed configuration, unlike the artificial metamaterial one, does not require the careful design of the material’s micro-structure, and hence is expected to be a practical candidate for obtaining a repulsive Casimir force.     

Influence of surface electronic structure on the Casimir force

Recent nonlocal microscopic theory of Casimir force which expresses the interaction energy between two metallic slabs in terms of surface polariton propagators calculated from diamagnetic and paramagnetic current-current response functions, sensitive to details of the surface electron density profiles and single-particle excitations on the surfaces, is used here to calculate various contributions to the Casimir energies for a silver film described by two different models. Current-current response functions are constructed from energy levels and wave functions obtained in two different models: jellium and Chulkov one-dimensional model potential, and the results are compared with the local plasmon model results. The results show how the details of such surface electronic structure modify Casimir force.     

Oscillating Casimir force between two slabs in a Fermi sea

The Casimir effect for two parallel slabs immersed in an ideal Fermi sea is investigated at both zero and nonzero temperatures. It is found that the Casimir effect in a Fermi gas is distinctly different from that in an electromagnetic field or a massive Bose gas. In contrast to the familiar result that the Casimir force decreases monotonically with the increase of the separation L between two slabs in an electromagnetic field and a massive Bose gas, the Casimir force in a Fermi gas oscillates as a function of L. The Casimir force can be either attractive or repulsive, depending sensitively on the magnitude of L. In addition, it is found that the amplitude of the Casimir force in a Fermi gas decreases with the increase of the temperature, which also is contrary to the case in a Bose gas, since the bosonic Casimir force increases linearly with the increase of the temperature in the region T < T_c, where T_c is the critical temperature of the Bose-Einstein condensation.     

THE CASIMIR FORCE BETWEEN POLARIZERS

The Casimir force between two parallel lincar polarizers oriented at an arbitrary angle is calculated. We compare two approaches, one by solving the field mode function in three-dimensional space with highly anisotropic dielectric slabs, the other by calculating the interaction between dipolcs induced by vacuum fluctuations in these slabs.     

Casimir Force Between Two Spatially Dispersive Dielectric Parallel Slabs

We investigate the Casimir force F between two parallel spatially dispersive semiconductor slabs, whose dielectric response function accounts for nonlocal effects. Nonlocal effects are induced by the presence of excitonic transitions in the semiconductor slabs for which our studies consider the A _n?=?1 exciton in CdS and the Z₃1s one in CuCl. In order to explore the nonlocal effects in the Casimir force, we first calculate the S and P polarized reflection coefficients of the excitonic slabs then we use them in the functional form of F. The slabs are considered as homogeneous, and nonhomogeneous media where the latter is a periodic system having a unit cell with period d. We present numerical calculations of F as a function of the vacuum gap of width L between the slabs, different slab thicknesses, and periods. Comparisons between numerical results obtained by using a nonlocal and a local theory show that the nonlocal effects are more significant at short separations of the slabs. F suffers a small decrease as a consequence of the energy absorption induced by the excitons.