共查询到20条相似文献,搜索用时 465 毫秒
1.
Munazza Zulfiqar Ali 《中国光学快报(英文版)》2012,(7):69-72
Wave propagation is studied in structures consisting of alternate left- and right-handed layers.Bragg gap and zero-n gap appear in different frequency regions of the structure.The periodicity of the structure is broken by simply reversing the order of the layers in one half of the structure,resulting in defect modes located inside the zero-n gap and Bragg gap.These modes can be made very narrow by adding more layers in the structure.The defect mode located inside the zero-n gap is sensitive to the symmetry of the structure and insensitive to the angle of incidence of the incoming radiation.Multiple modes are also generated inside the gaps by repeating the structural pattern.Thus,a simple structure can be used for single and multiple modes that are important for different applications. 相似文献
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We investigate the nanogap and polarization-resolved excitation of gap plasmon modes using terrace-stepped hexagonal boron nitride (hBN) sandwiched between Ag nanowires and Au substrates for a metal–insulator–metal gap structure. The gap plasmon modes in the proposed hybrid structure are dominantly excited by a P-polarized incident light, which is supported by full-wave numerical simulations. Plasmon mode evolution for various hBN spacer thicknesses ranging from 5 to 90 nm shows that optical signals acquired via unpolarized dark-field mapping spectroscopy are primarily due to the optical scattering of the P-polarized incident light. Moreover, this plasmonic mode changes significantly from gap plasmon mode to Fabry–Perot-type resonance in a hBN thickness of 50–90 nm. Our analysis reveals that the proposed hybrid structure based on Ag nanowires and stepped hBN provides a well-defined gap thickness and is a robust platform for analyzing gap plasmon modes. 相似文献
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We analytically study the nonlinear localized gap modes in a
one-dimensional atomic chain with uniform atomic mass but two periodically
alternating force constants between the nearest neighbors by means of
a quasi-continuum approximation. This model simulates a row of atoms
in the <111> direction of a diamond-structure type of crystals or
molecular crystals with alternating double and single bonds. For this
lattice system, we find that the harmonic plus quartic anharmonic terms
of inter-site potential produce a new type of nonlinear localized gap modes
with a slightly asymmetry distribution of atomic displacements. These localized
gap modes are somewhat different from widely studied localized gap
modes with a symmetry atomic displacement distribution in diatomic ion lattices. 相似文献
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We used an asymmetric layered system functioning as a plasmon waveguide coupler to couple surface plasmon modes with gap plasmon
modes. The planar system was analyzed by the transfer matrix method to design the optical dimensions of the system. We simulated
the effective mode indexes and H-field distribution of the coupled modes, for different gap widths and refractive indexes. For the calculated modes the propagation
lengths were calculated. Furthermore, a sample structure was fabricated and odd gap plasmon modes were excited with a coupling
prism in an attenuated-total-reflection (ATR) configuration. The mode index measurement showed good agreement with the simulation
data. 相似文献
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Zhengyan Deng Yongjin Yin Shengyang Yang Cai-Feng Wang Su Chen 《Applied Physics A: Materials Science & Processing》2013,112(3):591-596
The surface plasmon resonance (SPR) modes and near field gap enhancement of bowtie nanoantennas with triangle void defects are studied numerically. According to the location of the defects, we classify them into four categories: inner, edge, base and vertex defects. It is concluded that inner and base defects have little impact on both SPR modes and gap enhancement while edge and vertex defects which lead to mode splitting have great impact on the gap enhancement with symmetry breaking. Specifically, the size and location of edge defects have a remarkable effect on the resonant modes, especially for the low-energy resonant mode. When the edge defect gets close to the gap, the gap enhancement increases even above that of bowties with no defects. These properties are instructive to the evaluation of the fabrication of bowtie nanoantennas. And, by careful control of the defect location, we can get useful resonant modes and increase the gap enhancement for applications such as broadband light harvesting, ultra-fast wavelength-sensitive photodetection and fluorescent detection for two or more targets. 相似文献
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构造了(AB)N(BA)N对称型两种单负材料交替一维光子晶体,利用传输矩阵法进行数值模拟.结果表明:这种单负交替对称型一维光子晶体具有一种特殊带隙结构,该带隙不敏感于入射角和晶格的无序性.在该带隙内出现了两个隧穿模,该隧穿模不敏感于入射角的改变和晶格的无序性,但能带及带隙内的隧穿模却敏感于晶格标度和周期数的变化;随着入射角的改变,带隙两侧的隧穿模趋于简并.这些特性对在利用此结构光子晶体设计双重超窄带滤波器时,具有一定的参考价值.
关键词:
光子晶体
单负材料
光子带隙 相似文献
10.
The transmission properties of one-dimensional photonic crystals containing double-negative and singlenegative materials are studied theoretically.A special kind of photonic band gap is found in this structure.This gap is invariant with scaling and insensitive to thickness fluctuation.But when changing the ratio of the thickness of two media.the width of the gap could be enlarged.The defect modes are analyzed by inducing a linear defect layer in the structure.It is found that the number of defect modes will increase when the thickness of the defect layer becomes larger. 相似文献
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Lucovsky, Brodsky, Burstein (LBB) have studied the behaviour of mixed crystals by setting up a criterion for the existence
of local mode frequencies in real crystals starting from a diatomic linear chain model. This, while successfully predicting
the one and two mode behaviour for some systems fails to predict the mixed mode behaviour. We propose a similar criterion
for the existence of gap modes, by demanding that the gap mode predicted by the diatomic linear chain model should lie within
the gap of the real three dimensional solid for its existence. It is shown that the gap modes for various systems calculated
using this criterion are in reasonable agreement with the experimental values. The infrared behaviour of mixed crystals has
to be determined by examining the existence of local as well as gap modes for the two end members of the system. This generalized
new criterion successfully predicts the mixed mode behaviour of III–V mixed crystals besides predicting the one and two mode
behaviour, observed in infrared absorption of mixed alkali halioes and III-V compounds. 相似文献
12.
《中国光学快报(英文版)》2016,(7)
The nonlocal effect on the spontaneous emission of a silver cuboid dimer is investigated using a local analog model. Magnetic as well as electric dipole excitations are introduced to excite different gap modes. The nonlocal response of electric and magnetic modes on various parameters of gap(width and refractive index) are investigated. Unidirectional radiation is achieved by the interaction between electric and magnetic modes in both local and nonlocal models. Compared to local simulations, the resonant wavelength is blue shifted and the spontaneous emission enhancement is weakened in the nonlocal model. The relative shifts of the resonant wavelengths get larger in smaller gaps with a higher refractive index. 相似文献
13.
We point out that electromagnetic one-way edge modes analogous to quantum Hall edge states, originally predicted by Raghu and Haldane in 2D photonic crystals possessing Dirac point-derived band gaps, can appear in more general settings. We show that the TM modes in a gyromagnetic photonic crystal can be formally mapped to electronic wave functions in a periodic electromagnetic field, so that the only requirement for the existence of one-way edge modes is that the Chern number for all bands below a gap is nonzero. In a square-lattice yttrium-iron-garnet crystal operating at microwave frequencies, which lacks Dirac points, time-reversal breaking is strong enough that the effect should be easily observable. For realistic material parameters, the edge modes occupy a 10% band gap. Numerical simulations of a one-way waveguide incorporating this crystal show 100% transmission across strong defects. 相似文献
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The pair modes due to Cl?, Br?, Na+W and Rbv impurities in KI have been investigated using the Greens function technique. Group theory is used to put the final results as solutions of (2 × 2) determinants which could be tried by a hand calculator. Even a mass defect approximation reproduced the gap modes due to chlorine pairs, but in all cases a small change in the force constant, deduced from fitting single impurity gap modes, was used. The Raman active modes in all these cases were also computed. 相似文献
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分析了含单负材料的光量子阱结构中的振荡透射模的性质.用两种单负(负介电常量或负磁导率)材料交替周期堆叠形成的两个光子晶体构造了一维光量子阱结构,该结构中仅其中一个光子晶体含有零有效位相带隙.数值计算结果发现,在零有效位相带隙内存在振荡透射模.通过改变井区域光子晶体内单负材料层的厚度及周期数,振荡透射模的数目、频率及频率间隔均可调节.振荡透射模对入射角度的依赖均很弱;随着入射角度的改变,缺陷模频率的相对改变量保持在0.02以下.该研究结果可用于设计多通道全向滤波器. 相似文献
16.
《Physics letters. A》2020,384(35):126889
We investigate the defect states arising in the Bragg and non-Bragg gaps by inserting a straight duct into a waveguide with periodically corrugated walls. In periodic waveguides, the Bragg gap is created by the interference of the same transverse modes whereas the different mode coupling leads to the non-Bragg one. Due to the involved high-order modes, there are two defect states observed in the non-Bragg gap while only one in the Bragg gap, indicating that transverse modes play a significant role in the creation of defect states. Furthermore, the frequency of each defect state highly relies on the defect geometries and their band widths can be optimized by the number of waveguide segments. The proposed transverse mode competition analysis reveals the mechanism of frequency shifting and provides an opportunity for guided wave control engineering, which would definitely benefit their applications in various functional devices, such as filters, sensors, and amplifiers. 相似文献
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多个单负材料缺陷一维光子晶体的孪生缺陷模 总被引:4,自引:0,他引:4
分析了含有多个单负材料缺陷层的一维光子晶体中缺陷模的性质。在两种单负(负介电常量或负磁导率)材料交替堆叠形成的一维光子晶体中,掺入了多个周期排列的单负材料缺陷层,得到在该光子晶体的零有效相位(zero-effective phase)带隙内存在孪生缺陷模。通过改变缺陷的数目或缺陷层的厚度,可调节缺陷模的频率间隔,但缺陷模的数目总保持为两个。计算结果显示,该孪生缺陷模的频率对入射角度的依赖较弱;随着入射角度的改变,缺陷模频率的相对改变量总保持在0.03以下。此外,对应缺陷模频率的电场在该光子晶体中传播时,将被强烈地局域在缺陷层与周期结构的交界面上。 相似文献
19.
Pailhès S Ulrich C Fauqué B Hinkov V Sidis Y Ivanov A Lin CT Keimer B Bourges P 《Physical review letters》2006,96(25):257001
Resonant magnetic modes with odd and even symmetries were studied by inelastic neutron scattering experiments in the bilayer high-Tc superconductor Y1-xCa+Ba2Cu3O6+y over a wide doping range. The threshold of the spin excitation continuum in the superconducting state, deduced from the energies and spectral weights of both modes, is compared with the superconducting d-wave gap, deduced from electronic Raman scattering in the B1g symmetry on the same samples. Above a critical doping level of delta approximately =0.19, both mode energies and the continuum threshold coincide. We find a simple scaling relationship between the characteristic energies and spectral weights of both modes, which indicates that the resonant modes are bound states in the superconducting energy gap, as predicted by the spin-exciton model of the resonant mode. 相似文献
20.
研究了双带型光子晶体中双V型四能级原子自发辐射的辐射谱.双V型四能级原子同时与真空热库和双带型光子晶体热库耦合.研究发现双V型四能级原子自发辐射谱中有三种不同原因可能引起的黑线:第一种是由于量子干涉效应;第二种是由于各向同性光子晶体带边处态密度具有奇异性;第三种是真空场中的量子干涉和光子晶体禁带内态密度为零共同作用的结果.通过移动光子晶体的带边位置,在各向同性光子晶体带边引入光滑因子,以及在光子晶体中引入缺陷等对这三种黑线的影响,对上述结果进行了分析和讨论.
关键词:
双带型光子晶体
双V型四能级原子
黑线 相似文献