张向东
一直致力于光子晶体和低维纳米结构中的物理特性及其应用的研究。
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 姓名：张向东
 目前身份：
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学术头衔：
博士生导师， 教育部“新世纪优秀人才支持计划”入选者
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学科领域：
力学
 研究兴趣：一直致力于光子晶体和低维纳米结构中的物理特性及其应用的研究。
张向东，教授，博士生导师。1998年4月中国科学院物理研究所博士毕业。1998年5月至2002年4月在香港科技大学物理系作访问学者,从事博士后研究。2002年8月任北京师范大学物理系教授。2004年获教育部《新世纪优秀人才支持计划》支助。多年来,一直致力于光子晶体和低维纳米结构中的物理特性及其应用的研究。到目前为止，已在国内外著名期刊上接收或发表论文50余篇。其中在Phys. Rev. Lett.、Appl. Phys. Lett. 和 Phys. Rev.三个期刊上31篇。论文被他人引用200余次，其中单篇最高他人引用次数为88次。近年来，申请人作为特约审稿人，一直在该研究领域为国际著名的物理期刊Phys. Rev. Lett.和Phys. Rev. B/E提供审稿意见。

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10
【期刊论文】Impact of Weak Localization in the Time Domain
张向东， S. K. Cheung， X. Zhang， Z.Q. Zhang， A. A. Chabanov， and A. Z. Genack
PHYSICAL REVIEWL ETTERS B, VOLUME 17 30 APRIL 2004，0001，（）：
1年11月30日
We find a renormalized "timedependent diffusion coefficient," Dt, for pulsed excitation of a nominally diffusive sample by solving the BetheSalpeter equation with recurrent scattering. We observe a crossover in dynamics in the transformation from a quasi1D to a slab geometry implemented by varying the ratio of the radius, R, to the length, L, of the cylindrical sample with reflecting side walls and open ends. Immediately after the peak of the transmitted pulse, Dtfalls linearly with a nonuniversal slope that approaches an asymptotic value for R/L→1. The value of Dtextrapolated to t→0 depends only upon the dimensionless conductance g for R/L→1 and only upon k '0 for R/L 1, where kis the wave vector and '0 is the bare mean free path.

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【期刊论文】Negative refraction of acoustic waves in twodimensional phononic crystals
张向东， Xiangdong Zhang a)， Zhengyou Liu
PHYSICSL RETTERS B, VOLUME 2 12 JULY 2004，0001，（）：
1年11月30日
Negative refraction of acoustic waves in twodimensional phononic crystals has been demonstrated through both analysis and exact numerical simulation. The methods to achieve this behavior have been discussed. A microsuperlens for acoustic waves has also been designed. It is shown that refractive devices based on phononic crystals behave in a manner similar to that of optical systems. Therefore, a negative square root of the effective density or negative refraction index for acoustic waves can be introduced to describe this phenomena very well as the case of electromagnetic waves in the photonic crystals.

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【期刊论文】Enlarging a photonic band gap by using insertion
张向东， Xiangdong Zhang， ZhaoQing Zhang， and LieMing Li， C. Jin， D. Zhang， B. Man， and B. Cheng
PHYSICAL REVIEW B, VOLUME 3 15 JANUARY 2000I，0001，（）：
1年11月30日
We propose a simple, systematic, and efficient method to enlarge the gap of a photonic crystal. In this method, we add a small fraction of a third component into the existing photonic crystal. The dielectric property of the third component as well as its insertion position in a unit cell are chosen according to the fieldenergy distribution of two Bloch states at the band edges. The method is very general. It can be applied to any microstructure and is independent of the dimensionality of the original photonic crystal. Thus, it opens up a way to engineer photonic band gaps. Here, we demonstrate the validity of this method explicitly in two dimensions for both s and p waves. We show that, for certain microstructures, absolute gaps can be significantly enlarged. The method is also demonstrated in microwave experiments.

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【期刊论文】Spinpolarized tunneling and magnetoresistance in ferromagnet/insulator
张向东， Xiangdong Zhang and BoZang Li， Gang Sun， FuCho Pu
PHYSICAL REVIEW B, VOLUME 56 1 SEPTEMBER 1997I，0001，（）：
1年11月30日
Based on the twoband model, we present a transfermatrix treatment of the tunnel conductance and magnetoresistance for tunneling through ferromagnet/insulator (semiconductor) single junctions and double junctions subject to a dc bias. Our results are qualitatively in agreement with the experimental measurements for the single junction. For the double junction, we find that there exists, spinpolarized resonant tunneling and giant tunnel magnetoresistance. The highest value of the magnetoresistance in a double junction can reach 90%. We anticipate that our results will stimulate some interest in experimental efforts in designing spinpolarized resonanttunneling devices.

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【期刊论文】Tunable nonnearfield focus and imaging of an unpolarized electromagnetic wave
张向东， Xiangdong Zhang
PHYSICAL REVIEW B 71, 235103 (2005)，0001，（）：
1年11月30日
We propose a simple and efficient method to engineer absolute negative refraction for both polarizations of electromagnetic wave in twodimensional photonic crystal by adding an additional component to the existing photonic crystal. The dielectric property of the additional component, as well as its insertion position in a unit cell, are chosen according to the fieldenergy distribution of Bloch states at the band edges. According to our design, the nonnearfield focus and images for both polarized waves at the same structure and parameters, explicitly following the wellknown wavebeam negative refraction law, can be realized.

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张向东， Xiangdong Zhang
PHYSICAL REVIEW B 71, 241102(R) (2005)，0001，（）：
1年11月30日
It is shown that the transmission resonance of acoustic waves for an incident wavelength larger than the period of the grating exists in acoustic gratings with very narrow slits similar to that of optical subwavelength systems. The results are obtained by multiplescattering numerical simulations. The physical origin for such an acoustic transmission resonance is also analyzed.

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【期刊论文】Negative Refraction and Imaging Using 12foldSymmetry Quasicrystals
张向东， Zhifang Feng， Xiangdong Zhang， ， * Yiquan Wang， ZhiYuan Li， Bingying Cheng， and DaoZhong Zhang
PHYSICAL REVIEW LETTERS PRL 94, 247402 (2005)，0001，（）：
1年11月30日
Recently, negative refraction of electromagnetic waves in photonic crystals was demonstrated experimentally and subwavelength images were observed. However, these investigations all focused on the periodic structure. Here, we report a new theoretical and experimental finding that negative refraction can appear in some transparent quasicrystalline photonic structures. The photonic quasicrystals (PQCs) exhibit an effective refractive index close to 1 in a certain frequency window. The index shows small spatial dispersion, consistent with the nearly homogeneous geometry of the quasicrystal. More interestingly, a superlens based on the 2D PQCs can form a nonnearfield subwavelength image whose position varies with the source distance. These properties make PQCs promising for application in a range of optical devices.

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张向东， Xiangdong Zhang and ZhaoQing Zhang*
PHYSICAL REVIEW B, VOLUME 65, 245115，0001，（）：
1年11月30日
The field distributions of reflected speckles arising from localized states inside the gap of disordered photonic crystals in two dimensions were studied through numerical simulations using the multiplescattering method. The statistics of the Lyapunov exponent of the transmitted waves were also studied. Similar to the case of disordered photonic crystals in one dimension, two types of localized states were found depending on the degree of disorder and the frequency inside the gap. Our simulation results indicate that the reflection statistics depend on whether or not the localized states are of the normal type. They also depend on whether the reflected angles are in the Bragg direction or not. For the nonBragg angles, we found that the intensity distribution arising from the normaltype localized states follows Rayleigh statistics, in agreement with random matrix theory. However, deviations from Rayleigh statistics were found for second type of localized states. The crossover behavior from nonRayleigh to Rayleigh statistics was studied as a function of the degree of disorder. By separating the field into coherent and diffuse parts, we have studied the statistics of field and phase distributions for both diffuse and total fields as well as their speckle contrasts. It is found that the crossover behavior is very similar to behavior in ballistic to diffusive wave propagation for the transmited waves and can be described by the randomphasorsum model (RPS). For the Bragg angle, nonRayleigh statistics were found for both kinds of localized states. The statisics are sensitive to the degree of disorder. It is found that both the RPS and K distribution have limited ranges of validity in this case.

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【期刊论文】Coherent backscattering of light in a strong localization regime
张向东， Xiangdong Zhang and ZhaoQing Zhang
PHYSICAL REVIEW B, VOLUME 65, 155208，0001，（）：
1年11月30日
Coherent backscattering (CBS) of light in a strong localization regime is studied with absorption/ amplification included. The CBS cones arising from strongly localized states inside the complete gaps of disordered photonic crystals have been observed by numerical simulations in two dimensions. The structure of the CBS cones can be described well by a theory that incorporates mean free paths, localization length, amplification/absorption length, and singleparticle scattering anisotropy. The excellent agreement between theory and simulations without any adjustable parameters makes it ossible to determine the localization length from a measured CBS cone, even in an absorbing medium.

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【期刊论文】Absolute photonic band gaps in 12fold symmetric photonic quasicrystals
张向东， Xiangdong Zhang， ZhaoQing Zhang， and C. T. Chan
PHYSICAL REVIEW B, VOLUME 63, 081105(R)，0001，（）：
1年11月30日
A recent publication [Nature (London) 404, 740 (2000)] claimed that absolute photonic gaps can be realized in 12fold quasicrystalline arrangement of small airholes in a matrix of silicon nitride or glass. The result is rather surprising since silicon nitride (n52.02) and in particular, glass (n51.45) have rather low refractive index. In this work, we have studied the transmission properties of the same systems by using the multiplescattering method. We found that the 12fold trianglesquare tiling is indeed very good for the realization of photonic gaps and we found absolute gaps in systems with airholes in dielectric, dielectric cylinders in air, and metal cylinders in air. However, for the case of airholes in a dielectric background, absolute gaps appear only when the dielectric contrast is sufficiently high, and both silicon nitride and glass have refractive indices below the threshold.

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