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Zhen Ye

Publications and source records attributed to Zhen Ye.

At least 73 records · Page 4Linked to original sources
arXiv2003

A simulation study of localization of electromagnetic waves in two-dimensional random dipolar systems

We study the propagation and scattering of electromagnetic waves by random arrays of dipolar cylinders in a uniform medium. A set of self-consistent equations, incorporating all orders of multiple scattering of the electromagnetic waves, is derived from first principles and then solved numerically for electromagnetic fields. For certain ranges of frequencies, spatially localized electromagnetic waves appear in such a simple but realistic disordered system. Dependence of localization on the frequency, radiation damping, and filling factor is shown. The spatial behavior of the total, coherent and diffusive waves is explored in detailed, and found to be comply with a physical intuitive picture. A phase diagram characterizing localization is presented, in agreement with previous investigations on other systems.

cond-mat.dis-nn↗
arXiv2003

Focusing of electromagnetic waves by periodic arrays of dielectric cylinders

By numerical simulations, we show that properly arranged two dimensional periodic arrays, formed by dielectric cylinders embedded in parallel in a uniform medium, can indeed act as an optical lens to focus electromagnetic waves, in accordance with the recent conjecture in the literature. The numerical simulations are based on an exact multiple scattering technique. The results suggest that the E-polarized waves are easier to be focused than the H-polarized waves. The robustness of the focusing against disorders is also studied. Comparison with the corresponding cases for acoustic waves is also discussed.

cond-mat↗
arXiv2003

Localization of electromagnetic waves in two-dimensional random dielectric systems

We rigorously calculate the propagation and scattering of electromagnetic waves by rectangular and random arrays of dielectric cylinders in a uniform medium. For regular arrays, the band structures are computed and complete bandgaps are discovered. For random arrays, the phenomenon of wave localization is investigated and compared in two scenarios: (1) wave propagating through the array of cylinders; this is the scenario which has been commonly considered in the literature, and (2) wave transmitted from a source located inside the ensemble. We show that within complete band gaps, results from the two scenarios are similar. Outside the gaps, however, there is a distinct difference, that is, waves can be blocked from propagation by disorders in the first scenario, but such an inhibition may not lead to inhibition or wave localization in the second scenario. The study suggests that the traditional method may be ambiguous in discerning localization effects.

cond-mat.dis-nn↗
arXiv2002

Questions of perfect lenses by left handed materials

We consider questions about the much discussed "perfect lenses" made by left handed materials. The transmission and reflection from a slab of left handed materials are investigated and the coefficients are obtained by the standard transfer matrix method. Possible limitations on such superlenses are explored. It is shown that the quality of the lenses can be significantly affected by the absorption that is necessarily present in the materials.

cond-mat.soft↗
arXiv2002

Theoretical analysis of the focusing of acoustic waves by two-dimensional sonic crystals

Motivated by a recent experiment on acoustic lenses, we perform numerical calculations based on a multiple scattering technique to investigate the focusing of acoustic waves with sonic crystals formed by rigid cylinders in air. The focusing effects for crystals of various shapes are examined. The dependance of the focusing length on the filling factor is also studied. It is observed that both the shape and filling factor play a crucial role in controlling the focusing. Furthermore, the robustness of the focusing against disorders is studied. The results show that the sensitivity of the focusing behavior depends on the strength of positional disorders. The theoretical results compare favorably with the experimental observations, reported by Cervera, et al. (Phys. Rev. Lett. 88, 023902 (2002)).

cond-mat↗
arXiv2002

Localization of classical waves in two dimensional random media: A comparison between the analytic theory and exact numerical simulation

The localization length for classical waves in two dimensional random media is calculated exactly, and is compared with the theoretical prediction from the previous analytic theory. Significant discrepancies are observed. It is also shown that as the frequency varies, critical changes in the localization behavior can occur. Possible reasons for the discrepancies are discussed.

cond-mat.dis-nn↗
arXiv2002

Are waves all localized in two dimensional random media?

It has been the dominant view for over two decades that all waves are localized in two dimensions for any given amount of disorder. Here, I would like to raise questions about this assertion. The discussion leads to the conclusion that there is a lack of the conclusive and definite support of the claim. Rather, the recent evidence tends to indicate that waves are not necessarily always localized in two dimensional random systems. Reasons are elaborated.

cond-mat.dis-nn↗
arXiv2002

Localization of electromagnetic waves in a two dimensional random medium

Motivated by previous investigations on the radiative effects of the electric dipoles embedded in structured cavities, localization of electromagnetic waves in two dimensions is studied {\it ab initio} for a system consisting of many randomly distributed two dimensional dipoles. A set of self-consistent equations, incorporating all orders of multiple scattering of the electromagnetic waves, is derived from first principles and then solved numerically for the total electromagnetic field. The results show that spatially localized electromagnetic waves are possible in such a simple but realistic disordered system. When localization occurs, a coherent behavior appears and is revealed as a unique property differentiating localization from either the residual absorption or the attenuation effects.

cond-mat.dis-nn↗
arXiv2001

Propagation inhibition and wave localization in a 2D random liquid medium

Acoustic propagation and scattering in water containing many parallel air-filled cylinders is studied. Two situations are considered and compared: (1) wave propagating through the array of cylinders, imitating a traditional experimental setup, and (2) wave transmitted from a source located inside the ensemble. We show that waves can be blocked from propagation by disorders in the first scenario, but the inhibition does not necessarily imply wave localization. Furthermore, the results reveal the phenomenon of wave localization in a range of frequencies.

cond-mat.dis-nn↗
arXiv2001

Statistics of Lyapunov exponent in one-dimensional layered systems

Localization of acoustic waves in a one dimensional water duct containing many randomly distributed air filled blocks is studied. Both the Lyapunov exponent and its variance are computed. Their statistical properties are also explored extensively. The results reveal that in this system the single parameter scaling is generally inadequate no matter whether the frequency we consider is located in a pass band or in a band gap. This contradicts the earlier observations in an optical case. We compare the results with two optical cases and give a possible explanation of the origin of the different behaviors.

cond-mat↗
arXiv2001

Two dimensional photonic crystals

The topology, the symmetry involving the shape of dielectric cylinders, and the lattice structure are among the most important ingredients in the architecture of photonic crystals. In this paper, we present a systematic derivation of the formulas which are needed in computing the photonic band structures of many commonly used two dimensional lattice structures and dielectric cylinders with various kinds of symmetries and rotations. Further the results are applied to arrays of hollow cross-shaped cylinders embedded in the alumina ceramic background. A large complete photonic band gap is found in the high frequency regime.

cond-mat↗
arXiv2001

Scaling behavior in wave localization

Wave localization is a ubiquitous phenomenon. It refers to situations that transmitted waves in scattering media are trapped in space and remain confined in the vicinity of the initial site until dissipated. Based on a scaling analysis, the localization behavior in two and three dimensions is studied. It is shown that the localization transition is possible in two dimensional systems, supporting the recent numerical results.

cond-mat.soft↗
arXiv2001

Theoretical analysis of acoustic stop bands in two-dimensional periodic scattering arrays

This paper presents a theoretical analysis of the recently reported observation of acoustic stop bands in two-dimensional scattering arrays (Robertson and Rudy, J. Acoust. Soc. Am. {\bf 104}, 694, 1998). A self-consistent wave scattering theory, incorporating all orders of multiple scattering, is used to obtain the wave transmission. The band structures for the regular arrays of cylinders are computed using the plane wave expansion method. The theoretical results compare favorably with the experimental data.

cond-mat.soft↗
arXiv2001

Acoustic scattering by a cylinder near a pressure release surface

This paper presents a study of acoustic scattering by a cylinder of either infinite or finite length near a flat pressure-release surface. A novel self-consistent method is developed to describe the multiple scattering interactions between the cylinder and the surface. The complete scattering amplitude for the cylinder is derived from a set of equations, and is numerically evaluated. The results show that the presence of the surface can either enhance or reduce the scattering of the cylinder, depending on the frequency, the composition of the cylinder, and the distance between the cylinder and the surface. Both air-filled and rigid cylinders are considered.

physics.ao-ph↗
arXiv2001

Acoustic Attenuation by Two-dimensional Arrays of Rigid Cylinders

In this Letter, we present a theoretical analysis of the acoustic transmission through two-dimensional arrays of straight rigid cylinders placed parallelly in the air. Both periodic and completely random arrangements of the cylinders are considered. The results for the sound attenuation through the periodic arrays are shown to be in a remarkable agreement with the reported experimental data. As the arrangement of the cylinders is randomized, the transmission is significantly reduced for a wider range of frequencies. For the periodic arrays, the acoustic band structures are computed by the plane-wave expansion method and are also shown to agree with previous results.

cond-mat.soft↗
arXiv2000

Acoustic radiation in randomly-layered structures

Radiation from acoustic sources located inside randomly-layered structures is studied using the transfer matrix method. It is shown that in contrast to the periodically layered cases where the radiation can be either enhanced or inhibited depending on the frequency, and the characteristics and the material composition of the structures, in the random structures the radiation is always inhibited. The degree of inhibition depends on the acoustic frequency, number of random layers, and the randomness and acoustic parameters of the structures. Both spherically and cylindrically random structures are considered. The results point to the possibility of designing sonic waveguide devices which will not suffer from the energy loss caused by radiation, thus allowing effective energy confinement or long-range energy propagation.

cond-mat↗
arXiv2000

Localize energy in random media: A new phase state

This Letter reports a new wave phenomenon. We show that wave energy can be stored in random media. Associated with such energy storage is a global collective behavior. The features depicted are so general that they may be observed in many random systems.

cond-mat↗