共查询到19条相似文献,搜索用时 156 毫秒
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研究非稀释极限下带壳的球形颗粒复合介质体系光学双稳的温度效应.其中带壳颗粒是由具有线性响应的核和非线性响应的壳层组成.由于复合体系中的空间局域场是不均匀的,所以应用自洽平均场理论,解析推导核内电场平方的空间平均值与外电场的关系表达式,并对不同温度及不同结构参数下的光学双稳进行了数值计算.结果表明,双稳与温度T、结构参数k和体积分数f有关.在k和f一定时,随温度的升高,双稳效应因上阈值减小、下阈值增大而逐渐减弱,直至双稳消失;在T和f一定时,随结构参数的增大,上、下阈值都增大,而上阈值的增速较大从而导致双稳区域宽度加大.
关键词:
带壳颗粒
复合介质
光学双稳
温度效应 相似文献
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非均匀介质球颗粒的等效介电常量 总被引:1,自引:0,他引:1
从求解拉普拉斯方程的边值问题出发,讨论了非均匀介质球颗粒的等效介电常量,给出了多种介质组成的多壳层介质球颗粒的等效介电常量的一般递推公式,推导了壳层的介电常量随半径连续变化的梯度介质球的等效介电常量的微分方程.并以壳层的介电常量为幂函数为例,得到了梯度壳层介质球的等效介电常量. 相似文献
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介电弥散和介电隔离率的温度非线性关系是弛豫铁电体的主要特征. 通过对掺杂成分以线性梯度递减的核壳结构进行热力学函数分析, 认为核壳结构能够在低温区保持较高的介电常数, 但不能导致介电隔离率与温度的非线性关系. 通过对不同浓度掺杂的铁电体扩散相变的比较, 认为掺杂浓度会影响晶粒掺杂成分的不均匀性, 在较宽的分布条件下会导致介电隔离率与温度的非线性关系. 因而在介电常数的峰值温度区域, 顺电相与铁电相的晶粒共存. 温度变化会影响两相比例及铁电畴的变化, 从而导致弛豫铁电体的介电弥散性. 核壳结构会增大介电弥散性. 铁电陶瓷的掺杂物种类、掺杂物浓度和烧结温度均会影响核壳结构的成分不均匀性和介电弥散性. 相似文献
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利用Maxwell-Garnett近似,并结合谱表示方法,理论研究了具有一般非线性的绝缘颗粒,无规则浸入液体主体基质复合体系的非线性光学性质-在弱非线性条件下,数值研究了体系的有效线性介电函数和光学非线性随体积分数的变化,并发现体系的线性介电函数比光学非线性更依赖于绝缘颗粒组分的体积分数-在一般非线性条件下,研究体系的有效介电函数随入射光强度的依赖关系,还研究了s方向和p方向极化的总反射率的行为-
关键词:
复合介质
谱表示
非线性光学性质 相似文献
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This paper investigates analytically the electric field distribution of graded spherical core-shell metamaterials, whose permittivity is given by the graded Drude model. Under the illumination of a uniform incident optical field, the obtained results show that the electrical field distribution in the shell region is controllable and the electric field peak’s position inside the spherical shell can be confined in a desired position by varying the frequency of the optical field as well as the parameters of the graded dielectric profiles. It has also offered an intuitive explanation for controlling the local electric field by graded metamaterials. 相似文献
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In this paper, tunable optical bistability that denotes the relationship between input intensity and output intensity is numerically investigated in the microwave frequency region based on the one-dimensional (1D) sandwich photonic structure consisting of a Kerr-type nonlinear material slab and two magnetized cold plasma layers. Results show that, in the case of TM-polarized electromagnetic wave, width and switching thresholds of the bistability loops are dependent on the working frequency, initial incidence angle, layer thickness, plasma density, and external magnetic field, which should be judiciously selected to obtain a required bistability behavior. Compared to the case of switch-down threshold, the switch-up threshold in the bistability loop is more sensitive to the changes of parameters. Through this study, the suggested 1D sandwich photonic structure is beneficial to the all-optical signal processing. 相似文献
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A. Schmidt M. Kunz I. Lacis A. Daunois C. Klingshirn 《Zeitschrift für Physik B Condensed Matter》1992,86(3):337-344
In this paper we present results on ZnSe and ZnTe optically bistable elements in connection with electrooptic effects. The behaviour of optical hysteresis under an applied electric field is studied and the electrical characteristics under illumination with monochromatic laser radiation are investigated. Influences of optical bistability on the photocurrent are measured and an attempt is made to explain the unusual behaviour of the current with respect to the absorbed amount of light, namely a switching down in photocurrent when the absorptive switching takes place. Towards this aim we report here for the first time on spatially resolved measurements of photoconductivity in ZnSe to investigate the influence of Schottky contacts on photothermal electrooptic bistability. Furthermore, we report also to our knowledge for the first time on the influence of the 3D-Stank effect on optical bistability. 相似文献
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The optical properties of MnAl films of different compositions, deposited at different substrate temperatures and in the thickness range 25 to 90 nm, are reported. The reflectance and transmittance are measured in the wavelength range 320–900 nm for near normal incidence of light. These measurements are used to calculate the optical constants namely, refractive index (n) and extinction coefficient (k). The wavelength and thickness dependence of these optical constants are reported. The optical measurements for films with higher Mn content and grown at higher substrate temperature reveal that n and k values are constant over a wide wavelength range (500–900 nm) showing high reflectance in the visible and near infrared region. 相似文献
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MA Chunsheng 《Chinese Journal of Lasers》1998,7(4):321-328
1IntroductionInrecentyearsnonlinearopticalwavesguidedbymultilayersystemsincludingmultiplequantumwel(MQW)structureshaveatracte... 相似文献
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We theoretically investigate the optical bistability, which one input signal allows two possible outputs, from single spherical/cylindrical nanoparticles and also nanoshells in the frame work of quasi-static formalism. It is shown that the bistability behavior greatly depends on several parameters such as the nanoparticle size, material and the surrounding dielectric environment. We demonstrated the width of the bistability region and also the bistable threshold depends on the geometrical parameters, and can be tuned by adjusting the size of nanoparticle, the shell thickness and the dielectric constant of the embedding medium. It is also shown that the optical bistable behavior depends strongly on the shape of plasmonic nanoparticles and nanoshells. However, these dependences of optical bistability of spherical/cylindrical nanoparticles and nanoshells on changing of their geometrical parameters can be used for realize optical switching and sensing purposes. 相似文献
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The discrete gap breathers (DGBs) in a one-dimensional diatomic chain with K2-K3-K4 potential are analysed. Using the local anharmonicity approximation, the analytical investigation has been implemented. The dependence of the central amplitude of the discrete gap breathers on the breather frequency and the localization parameter are calculated. With increasing breather frequency, the DGB amplitudes decrease. As a function of the localization parameter, the central amplitude exhibits bistability, corresponding to the two branches of the curve ω = ω(ζ). With a nonzero cubic term, the HS mode of DGB profiles becomes weaker. With increasing K3, the HS mode of DGB profiles becomes weaker and a bit narrower. For the LS mode, with increasing K3, the central particle amplitude becomes larger, and the DGB profile becomes much sharper. But, as k3 increases further, the central particle amplitude of the LS mode becomes smaller. 相似文献
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Mahendra K. Verma 《Journal of Turbulence》2016,17(12):1112-1141
We present a magnetohydrodynamic (MHD) shell model suitable for computation of various energy fluxes of MHD turbulence for very small and very large magnetic Prandtl numbers Pm; such computations are inaccessible to direct numerical simulations. For small Pm, we observe that both kinetic and magnetic energy spectra scale as k?5/3 in the inertial range, but the dissipative magnetic energy scales as k?11/3exp?(? k/kη). Here the kinetic energy at large length scale feeds the large-scale magnetic field that cascades to small-scale magnetic field, which gets dissipated by Joule heating. The large-Pm dynamo has a similar behaviour except that the dissipative kinetic energy scales as k?13/3. For this case, the large-scale velocity field transfers energy to the large-scale magnetic field, which gets transferred to small-scale velocity and magnetic fields; the energy of the small-scale magnetic field also gets transferred to the small-scale velocity field, and the energy thus accumulated is dissipated by the viscous force. 相似文献