共查询到20条相似文献,搜索用时 15 毫秒
1.
We have theoretically explored the negative refraction (NR) in one-dimensional plasma photonic crystals (PCs) consisting of plasma and dielectric materials. By using the transfer matrix method and Bloch theorem, we have studied the group velocity and we have obtained the NR in plasma PCs with the help of the group velocity. The results show that plasma PCs can also exhibit the NR although they have a periodically modulated positive permittivity ? and permeability μ. It is also shown that the NR in plasma PCs exhibits difference behaviour in different frequency regions, ω < ωp and ω > ωp, respectively. The parameter dependence of the effects is also examined and discussed. 相似文献
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Negative refraction in photonic crystals 总被引:4,自引:0,他引:4
We demonstrate that light propagation in strongly modulated 2D/3D photonic crystals (PhCs) becomes refraction-like in the vicinity of the photonic bandgap, which is contrary to the fact that light propagation in weakly modulated PhCs is very different from refraction and thus the definition of refraction index becomes meaningless. Such a crystal behaves like a material having an effective refractive index controllable by the band structure. This situation is analogous to the effective-mass approximation in electron-band theory. The propagation states having a negative effective index exhibit unusual properties, such as mirror-like imaging effect, image-transfer effect. These properties are confirmed by finite-difference time-domain simulations. 相似文献
3.
Zhang Xiang-dong 《Frontiers of Physics in China》2006,1(4):396-404
The negative refraction of electromagnetic waves in photonic crystals was recently demonstrated experimentally, and the physical
properties were analyzed. Microsuperlenses based on two-dimensional photonic crystals were designed and the subwavelength
images were observed. In this review, after providing a brief history of the research related to the above phenomena, we will
summarize our research works in this field including the method of creating a negative refraction region, generating an absolute
negative refraction, the focusing of unpolarized electromagnetic waves, and the effect of interface and disorder on the image
by the two-dimensional photonic crystal flat lens. The discussion on the negative refraction and the focusing by high symmetric
quasicrystals is also presented. 相似文献
4.
We have discussed theoretically the negative refraction in finite
one-dimensional (1D) photonic crystals (PCs) composed of alternative
layers with high index contrast. The frequency bands of negative
refraction are obtained with the help of the photonic band structure,
the group velocity and the power transmittance, which are all
obtained in analytical expression. There shows negative transverse
position shift at the endface when negative refraction occurs, which
is analysed in detail. 相似文献
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结合波状结构二维(2D)光子晶体(PC)与入射介质两者的等频面结构分析了PC内部的负折射现象,采用时域有限差分(FDTD)方法模拟了高斯光束在波状结构2DPC内的负折射,分别得到了折射角/入射角以及折射角/入射波长之间的关系曲线,当入射角为45°,入射波段在1485—1530nm区域时,波状结构2DPC的负折射角与入射波长近似呈线性变化关系,并带有明显的PC超棱镜效应,采用端面投影方法对波状结构2DPC的入射端面和出射端面进行处理,改善了负折射时的透过率.
关键词:
光子晶体
负折射
等频面 相似文献
7.
We report our experimental results on two-dimensional left-handed metamaterials (LHM) exhibiting negative refraction and subwavelength imaging. Transmission and reflection spectra of LHM are studied and a left-handed transmission band is observed at the frequencies where both dielectric permittivity and magnetic permeability are negative. Impedance matching is verified both with the experiments and simulations. The two-dimensional LHM structure is verified to have a negative refractive index. We employed three different methods to observe negative refraction; refraction through prism-shaped LHM, beam shifting method, and phase shift experiments. We further demonstrated subwavelength imaging and resolution using LHM superlenses. The effect of thickness on the resolving power is investigated experimentally. 相似文献
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采用磁化等离子体的分段线性电流密度卷积时域有限差分(PLCDRC-FDTD)算法研究具有单一缺陷层的一维磁化等离子体光子晶体的缺陷模特性. 从频域角度分析得到微分高斯脉冲的透射率,并讨论该光子晶体的缺陷层厚度、位置、周期常数和等离子体参数对其缺陷模的影响. 结果表明,改变位置和周期常数不会影响缺陷模的频率,改变缺陷层的厚度可以增加缺陷模数,改变等离子体参数能同时影响缺陷模的频率和峰值.
关键词:
磁化等离子体光子晶体
光子晶体
缺陷模
时域有限差分法 相似文献
10.
Cheng-Yang Liu Nai-Wen Zhang Hung-Wen Wang Lien-Wen Chen 《Physica B: Condensed Matter》2009,404(21):4060-4070
Photonic crystals (PCs) have many potential applications because of their ability to control light-wave propagation. We have investigated the electromagnetic wave propagation inside an elliptic rod PC slab by means of finite-difference time-domain simulations. The band structure of the PC composed of elliptic rod in the square and triangular lattices is studied by solving Maxwell's equations using the plane wave expansion method. Numerical simulations show that the refractive angle can be tuned greatly by rotating the directors of elliptic rod in the PC slab. Furthermore, an optical switch based on elliptic rod PC structures with nematic liquid crystals was proposed. In the on/off switching system, the partial band gap can be controlled when the normalized operation frequency is 0.28. The modulation induced by liquid crystals created a sharp switching in the photonic devices. Such a mechanism of negative refraction PCs should open up a new application for designing components in photonic integrated circuits. 相似文献
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We report on the negative refraction and left-handed behavior of two-dimensional photonic crystals. For the triangular two-dimensional photonic crystals there are two saddle points and a key point in the first Brillouin zone for the second band, which play important role to determine the refraction phenomena. There is no determined relation between the left-handed behavior and the negative refraction. The refraction phenomena depend on the band structure and the configuration of the incident light. For the first configuration, the first Brillouin zone can be divided into three parts. In part I there are negative refraction and left-handed behaviors. In part II there are normal refraction and left-handed behaviors. In part III there are normal refraction and right-handed behaviors. For the second configuration, the first Brillouin zone can only be divided into two parts. For these complex refraction phenomena, it is meaningless to define the phase refractive index, and it is necessary to define the effective refraction index by a Snell-like formula, and the value of the effective index is determined by the configuration and the band structure. 相似文献
13.
We present a simple and complete approach to determining the directions and amplitudes of rays propagating through arbitrary systems of homogeneous and/or uniaxial materials. In the process we extend the work of Gu and Yen to full generality. 相似文献
14.
Based on transmission spectra, optical switching effect of equivalent negative refractive photonic crystals (PCs) composed of a triangular array of air cylinders in a GaAs matrix is studied by the finite-difference time-domain (FDTD) method in this paper. The mechanism of wave resonance is probed and the propagation of optical waves in the PCs is described in terms of effective refraction index and Bloch waves. Our numerical results show that the probability of spontaneous radiation would be enhanced extremely under the influence of Bloch resonance waves, stimulated emission and photon tunnel effect, resulting in the optical waves being localized greatly in the PCs at particular frequencies. In addition, we found that the position of transmission peaks, with values much greater than unit, can be controlled by tuning the central frequency of the waveguide source. It means that photon current in the PCs can also be controlled to optimize transmission properties of PCs, so as to meet the requirements of novel optical devices based on PCs, such as all-optical switches. 相似文献
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为了得到分辨率更好的平板透镜,对此进行了研究。利用有限元的方法研究了由水/水银材料组合的二维蜂窝结构声子晶体平板透镜的负折射成像特性,通过数值仿真计算了声子晶体的能带结构、等频色散曲线,模拟了点源成像,并且利用高斯波束验证了声子晶体平板透镜的负折射现象,得到了有效折射率neff =-1的成像。对比相同材料的正方晶格和三角晶格而言,该模型的成像效果更佳。为了改善成像分辨率,还在原来的模型上进行了改进,得到了分辨率约为0.37λ的亚波长像。 相似文献
17.
��־�� 《核聚变与等离子体物理》2018,38(1):117-124
在理想条件下,为了研究等离子体回旋频率、等离子体频率、等离子体层厚度、周期常数和入射角在TM模式下对一维磁化等离子体光子晶体的非互易特性的影响,用利用传输矩阵法计算得到的TM波正向和反向传播的透射率来研究其非互易特性。研究结果表明,增加等离子体回旋频率和入射角度能够改善非互易特性;而一味地增加等离子体频率和等离子体层厚度将会使得非互易传播特性变得恶化;增加周期常数不能明显地改善非互易传播特性,但是通过改变外加磁场的施加方式能够改善其非互易特性。 相似文献
18.
S. Guenneau S. Anantha Ramakrishna S. Enoch Sangeeta Chakrabarti G. Tayeb B. Gralak 《Photonics and Nanostructures》2007,5(2-3):63-72
Negative refractive index materials are known to be able to support a host of surface plasmon states for both polarizations of light. This makes possible unique effects such as a perfect lens. Checkerboards consisting of alternating cells of positive and negative refractive index represent a very singular situation in which the density of modes diverges at the corners. This raises the question as to whether such effects will still be observed in a real dissipative system of finite size. We have considered several aspects of such structures including these and symmetry aspects (rectangular against triangular checkerboards). We have also studied silver checkerboards whose transverse extent is finite. Negative refractive index checkerboards bring new electromagnetic paradigms both through the intriguing possibilities they appear to offer, and the challenges they present to our understanding of the diffraction process. Most intriguing of all is the possibility of a triangular checkerboard lens whose resolution is limited not by wavelength, but only by the losses in the constituent materials, while a ray picture suggests it behaves as a perfect mirror. The resolution of this lens increases without limit as the losses tend to zero as shown by the generalized lens theorem. We finally show that light confinement can be achieved to certain extent using dielectric triangular photonic crystal (PC) checkerboards displaying the all-angle-negative-refraction (AANR) within the Bragg regime in p polarization. Effectively even a single rectangular or triangular PC can act as an open resonator that confines light in its neighborhood. This cloaking effect has been previously observed in PC slabs displaying the AANR effect. We show that the cloaking is enhanced for three triangular PC wedges sharing a vertex and further improved for 12 triangular PC wedges arranged in a checkerboard fashion. 相似文献
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采用平面波展开法和时域有限差分法研究了二维色散和各向异性磁化等离子体光子晶体的色散特性.当波矢在周期平面时,由于外加磁场的作用使TE模的色散曲线出现两个不同区域的平带,改变磁场的大小不但可以控制平带的位置,而且可以控制光子带隙的位置和大小.增大背景材料的介电常数,可以形成全方向光子带隙,随着背景材料介电常数的增加,带隙的中心位置降低但带隙宽度增加.当波矢偏离周期平面时,色散曲线不再分为TE和TM模,随着非周期平面波矢的增加,带隙位置上移,带隙宽度先增加随后基本保持不变. 相似文献