共查询到20条相似文献,搜索用时 15 毫秒
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《Waves in Random and Complex Media》2013,23(4):245-263
Abstract Second-order polarization correlation functions, both theoretical and experimental, are presented for optical waves propagating through a highly random multiple-scattering two-dimensional (2D) medium. For normal incidence and scattering, a 2D medium is found to be fully described by two material parameters, one of which is complex. Simple formulae are developed for these parameters in terms of the anisotropy of the medium and the scattering mean free path. General theoretical expressions are given for polarized and unpolarized correlation functions and also for the intensity statistics of the scattered light for arbitrary input polarization states. Experimental data are presented for both types of correlation function and for the intensity statistics, and are found to be in reasonably good agreement with the theory. 相似文献
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J. D. Gunton 《Journal of statistical physics》1984,34(5-6):1019-1037
A review is given of recent developments involving the dynamics of random interfaces formed in the evolution of metastable and unstable systems. Topics which are discussed include interface growth and nonequilibrium dynamical scaling. The possibility of there being dynamical universality classes in first-order phase transitions is also discussed. There are a large number of systems of experimental interest which include binary alloys, binary fluids, and polymer mixtures. Other systems studied by computer simulation include the kinetic Ising, Potts, andZ
N
models.Work supported by NSF grant No. DMR-8013700. 相似文献
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《Comptes Rendus Physique》2013,14(8):641-650
We discuss the universal dynamics of elastic interfaces in quenched random media. We focus on the relation between the rough geometry and collective transport properties in driven steady-states. Specially devised numerical algorithms allow us to analyze the equilibrium, creep, and depinning regimes of motion in minimal models. The relevance of our results for understanding domain wall experiments is outlined. 相似文献
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We continue the analysis of hierarchical interfaces in random media started in earlier work. We show that from the estimates on the renormalized random variables established in that work, it follows that these models possess unique Gibbs states describing mostly flat interfaces in dimensionD > 3, if the disorder is weak and the temperature low enough. In the course of the proof we also present very explicit formulas for expectations of local observables. 相似文献
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S. Stepanow 《Annalen der Physik》1992,504(6):423-439
The time evolution of an interface in a disordered media is described by using the propagator method. The method enables one to represent the perturbation expansions of different quantities characterizing the interface by means of diagrams which are familiar from the field theory. By the analysis of the divergences in the vicinity of the critical dimension dc = 4 we found that the regularization of the theory demands the renormalization of the mobility and all moments of the disorder correlator excepting the zero one. The renormalization group (RG) calculations of the average velocity of the interface, the roughness, and the functional RG equation of the disorder correlator are presented to order ? = 4 - d. The latter coincides with the result obtained by D. S. Fisher in the equilibrium case. The RG equations have a pole at the value of the driving force, which coincides with the value of the threshold below which the interface becomes pinned as predicted by Bruinsma and Aeppli. The behavior of the mobility in the vicinity of the pole is discussed. 相似文献
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A. Yu. Vetluzhsky 《Journal of Experimental and Theoretical Physics》2009,109(2):302-306
The localization of electromagnetic waves in a two-dimensional random medium composed of strong scatterers is studied theoretically.
It is shown that an allowance for the spatial radiation intensity distribution inside the medium, along with an analysis of
the distance dependence of the transmission coefficient, is needed to reveal the localization states in media of finite extent. 相似文献
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采用时域有限差分法数值求解Maxwell方程组,分析了平面随机介质中光波模式的频谱时间演化特性.随机介质的特征可以用散射颗粒的随机构形、介质参数(如颗粒的尺寸和填充率等)以及介质形态等因素来描述.这些因素决定了随机介质在准稳态下模式的频率特性与数量,但具有不同因素的随机介质中模式的产生、选择与演化,具有大致相同的特征与速度.平面随机介质的这些冷腔特性,与传统光腔中模式的产生、选择和演化的特征非常相似.
关键词:
激光物理
随机激光器
无序介质中的光学特性 相似文献
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Jiantao Lü 《中国光学快报(英文版)》2006,4(4)
The pumping rate dependence of the peak intensity of the individual lasing mode in two-dimensional (2D) active random media is investigated. The results show that these modes have a typical threshold gain behavior and different threshold pumping rates. There exists a certain correspondence between the mode's threshold pumping rate and its lifetime, and the longer the lifetime is, the lower the threshold is. 相似文献
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We study numerically the interaction of spatially localized modes in strongly scattering two-dimensional (2D) media. We move eigenvalues in the complex plane by changing gradually the index of a single scatterer. When spatial and spectral overlap is sufficient, localized states couple, and avoided level crossing is observed. We show that local manipulation of the disordered structure can couple several localized states to form an extended chain of hybridized modes crossing the entire sample, thus changing the nature of certain modes from localized to extended in a nominally localized disordered system. We suggest such a chain in 2D random systems is the analog of one-dimensional necklace states, the occasional open channels predicted by Pendry [Physics 1, 20 (2008).] through which the light can sneak through an opaque medium. 相似文献
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We elucidate a long-standing puzzle about the nonequilibrium universality classes describing self-organized criticality in sandpile models. We show that depinning transitions of linear interfaces in random media and absorbing phase transitions (with a conserved nondiffusive field) are two equivalent languages to describe sandpile criticality. This is so despite the fact that local roughening properties can be radically different in the two pictures, as explained here. Experimental implications of our work as well as promising paths for future theoretical investigations are also discussed. 相似文献
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Molecular dynamics simulations of mobile particles confined in disordered immobile particles are carried out. Slow dynamics
in random media are characterized by two types of dynamics: Type B dynamics for large mobile particle density and Type A dynamics for small mobile particle density. The crossover from Type A to B dynamics is studied by the mean square displacement and the density correlation function. Our results are qualitatively consistent
with the results of recent numerical and theoretical studies on relevant spatially heterogeneous systems. We also investigate
the effect of random matrix generation on the dynamics of mobile particles in order to examine the reentrant transition predicted
by the recent mode-coupling theory. Our simulations demonstrate that the diffusion of the mobile particles largely depends
on the protocol of the random matrix generation and that the reentrant transition is observed for a particular protocol. 相似文献
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Qingquan Zhang Kejia Wang Hai Liu Xiaodong Wang Zeming Du 《Optics Communications》2008,281(14):3856-3860
For a set of two-dimensional passive random media that have the same randomness and different shapes, the effects of morphology on the time evolution of the power spectrum of the localized modes supported by the media are investigated. The results demonstrate that the evolving process of the spectrum, the lifetime of short-lived modes and the amount of long-lived modes are morphological-dependent, while the lifetime of long-lived modes is morphological-independent. The denser the medium is, the quicker the evolving process and the shorter the lifetime of the short-lived modes are. Single-mode operation is more possible and occurs more early for a denser medium, which is of practical importance for proposing a mode-selecting technique for random lasers. 相似文献
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We prove that in dimensiond2 translation-covariant Gibbs states describing rigid interfaces in a disordered solid-on-solid (SOS) cannot exist for any value of the temperature, in contrast to the situation ind3. The proof relies on an adaptation of a theorem of Aizenman and Wehr. 相似文献
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Lasing in random media 总被引:2,自引:0,他引:2
Hui Cao 《Waves in Random and Complex Media》2003,13(3):R1-R39
A random laser is a non-conventional laser whose feedback mechanism is based on disorder-induced light scattering. Depending on whether the feedback supplied by scattering is intensity feedback or amplitude feedback, random lasers are classified into two categories: random lasers with incoherent feedback and random lasers with coherent feedback. A brief survey of random lasers with incoherent feedback is presented. It is followed by a review of our recent experimental work on random lasers with coherent feedback, including measurement of the lasing threshold, lasing spectra, emission pattern, dynamical response, photon statistics, speckle pattern and the investigation of relevant length scales. Large disorder leads to spatial confinement of the lasing modes, that is the foundation for the micro random laser. Some theoretical models of random lasers with coherent feedback are briefly introduced. The study of random lasers improves our understanding of the interplay between light localization and coherent amplification. 相似文献
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