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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
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对一维全息底片运用光子晶体的概念,利用平面波展开法和传输矩阵法,数值计算了介电常数余弦调制的一维全息光子晶体结构的带隙,主要针对全息记录材料为重铬酸盐明胶时设置了计算用参数,计算结果表明对于折射率周期性渐变的一维全息晶体结构同样具有一般光子晶体的带隙,进而研究了带隙的特点.发现禁带宽度随着所使用的记录介质折射率的增加而减小,随着介质折射率调制的增加而增加;带的位置随着介质折射率的增加而移向低频,随着介质周期长度的增加移向低频,折射率调制的改变基本不影响禁带位置. 相似文献
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最近研究表明,两束交叉激光脉冲在等离子体中传播时,可以诱导生成周期等离子体密度调制(或称等离子体布拉格光栅). 分别利用传输矩阵法和耦合模理论,推导了激光斜入射时等离子体光栅的色散关系. 两种方法均表明,均匀等离子体光栅存在着光子带隙结构,并且在带隙附近有强烈的色散. 当激光斜入射时,带隙结构会呈现不同的偏振特性:S偏振光的带隙宽度随着入射角的增大而逐渐变宽,而P偏振光的带隙宽度随着入射角的增大先迅速变窄,在布儒斯特角入射时带隙消失,然后又随着入射角的增大而迅速变宽. 超宽的光子带隙和超高的激光损伤阈值,使得等离子体光栅有望成为一种新型的操纵强激光脉冲的光子器件.
关键词:
等离子体光栅
传输矩阵法
耦合模理论
光子带隙 相似文献
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本文利用集中质量法对弹性纵波在一维指数形截面有限周期声子晶体中的传播进行了研究, 得到了频率响应函数的表达式. 与一维等截面的声子晶体相比, 指数形变截面声子晶体带隙内的衰减值随着输出端截面积的增大而减小, 同时带隙的起始频率降低而截止频率升高, 也即带隙的宽度会得到拓展. 晶格常数和材料组份比变化时, 变截面声子晶体带隙的起始频率和截止频率的变化趋势与等截面时的声子晶体相同. 希望本文的研究能够推动声子晶体在减振降噪等领域中的应用. 相似文献
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利用MPB软件和MEEP软件对一维光子晶体带隙结构及透射谱进行了仿真与实验研究.讨论了不同介质填充比和介质相对介电常数对光子晶体带隙结构的影响.仿真结果表明,当高相对介电常数介质的填充比增大时,或高相对介电常数增大时,光子晶体带隙的中心频率缓慢减小,带隙宽度呈先增大后减小的趋势,存在一极大值点.采用高相对介电常数介质薄板[钛酸钡(BaTiO<,3>)粉末混合聚二甲基硅氧烷(PDMS)胶体]和泡沫薄板周期性排列组成一维光子晶体.实验上制得了高低介质相对介电常数分别为4.5和1,填充比为1:1,晶格常数为10 mm,周期数为5的光子晶体,并测量出该光子晶体的微波透射谱.测量结果表明,在8~12 GHz的微波频段,该光子晶体的带隙中心频率为9.3 GHz,带隙宽度为500 MHz. 相似文献
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木堆结构三维光子晶体带隙特性 总被引:1,自引:0,他引:1
基于平面波展开法研究木堆结构三维光子晶体带隙特性.用硅材料构成木堆结构三维光子晶体,改变结构中木条的宽度和长度,得到当木堆条宽度为5μm,高度为7μm时形成的带隙结构较宽,在0.2899-0.3804Hz,带隙宽度为0.0905Hz.改变构成木堆结构三维光子晶体的材料,得到锗材料构成木堆结构三维光子晶体带隙结构在0.2585-0.3500Hz,带隙宽度为0.0915Hz,带隙相比硅材料和碳化硅材料较宽.研究结论为三维光子晶体的制备提供参考. 相似文献
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The charge-density-wave phase of TiSe(2) was studied by angle-resolved photoelectron spectroscopy and resistivity measurements investigating the influence of the band gap size and of a varying population of the conduction band. A gradual suppression of the charge-density-wave-induced electronic superstructure is observed for a variation of the band gap in the ternary compounds TiC(x)Se(2-x) with C=(S,Te) as well as for an occupation of only the conduction band by H(2)O adsorption-induced band bending. These observations point to an optimum band gap and support an excitonic driving force for the charge-density wave. 相似文献
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Frank J. Owens 《Molecular physics》2013,111(21-23):2441-2443
The electronic properties, band gap and ionization potential as well as the energies of the singlet and triplet states of zigzag and armchair graphene nanoribbons are calculated as a function of the number of oxygen atoms on the ribbon employing density functional theory at B3LYP/6-31G* level. The calculated band gaps indicate that both structures are semiconducting. The band gap of the armchair ribbons initially decreases followed by an increase with oxygen number. For zigzag ribbons the band gap decreases with increasing oxygen number whereas the ionization potential increases with oxygen content. In both armchair and zigzag ribbons the ionization potential shows a gradual increase with the number of oxygen atoms. Some of the oxygenated ribbons calculated have triplet ground states and have the density of states at the Fermi level for spin down greater than spin up suggesting the possibility they may be ferromagnetic semiconductors. 相似文献
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The photonic crystal is an artificial material with periodic dielectric constant and the key factor to preserve their band features is its periodicity. When the number of periods of photonic crystal is decreased the photonic band gap cannot prevent the light of the corresponding frequencies from propagating in photonic crystal, in another word, photonic band gap will be failure. The minimum periods of photonic crystal device which can keep photonic band gap effective in miniaturization process is analyzed, the transmittance spectrum is calculated by the Finite-difference time-domain algorithm (FDTD) [1], the minimum periods is got in the simulation and the reason which affects the minimum periods is analyzed in this paper. 相似文献
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Based on the non-symmetric transmission-line method, the band gap structure of disordered chiral photonic crystals (CPC) has
been investigated. The influence of the chiral parameters, the disorder, the periods and the refractive index on the band
gap structure has been discussed. It is found that the photonic band gap (PBG) in CPC is more obvious than that in the conventional
photonic crystals, and the PBG can be increased by increasing the periods or the contrast of the refractive index of the two
media. It is also found that the existence of disorder will influence the band edge of the PBG, and such influence will increase
with the increment of periods or the contrast of the refractive index of the two media. 相似文献
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采用基于密度泛函理论的第一性原理方法,对二维BC2N薄片的结构稳定性和电子性质进行了系统的研究.计算了BC2N化合物16种可能的二维单层结构.对它们的能带结构分析发现,对称性最高的构型与石墨烯一样是一种半金属,而其他二维结构则为有不同带隙的半导体,其中最稳定的构型是带隙值为1.63 eV的直接带隙半导体.对最稳定构型的差分电荷密度分析和Bader分析发现:在最稳定的构型中,C–C键、C–N键、C–B键和B–N键主要以共价键的形式呈现,也具有比较明显的离子性.在应力作用下最稳定构型的单层BC2N的带隙宽度会发生变化,压缩时带隙变宽,而拉伸时带隙变窄,但仍然为直接带隙半导体.
关键词:
2N')" href="#">BC2N
单层原子薄片
电子结构
从头计算 相似文献
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《中国科学:物理学 力学 天文学(英文版)》2020,(3)
PbI_2/MoS_2, as a typical van der Waals(vdW) heterostructure, has attracted intensive attention owing to its remarkable electronic and optoelectronic properties. In this work, the effect of defects on the electronic structures of a PbI_2/MoS_2 heterointerface has been systematically investigated. The manner in which the defects modulate the band structure of PbI_2/MoS_2, including the band gap, band edge, band alignment, and defect energy-level density within the band gap is discussed herein. It is shown that sulfur defects tune the band gaps, iodine defects shift the positions of the band edge and Fermi level, and lead defects realize the conversions between the straddling-gap band alignment and valence-band-aligned gap, thus enhancing the light-absorption ability of the material. 相似文献
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基于平面波展开法,理论分析了晶格结构、填充率、介电常数比等因素对fcc,diamond,woodpile三种三维光子晶体典型结构完全禁带的影响.三种结构中,fcc结构由于高对称性导致的能级简并,只适用于密堆积排列的反蛋白石结构;diamond结构非常容易产生高带隙率的完全禁带,并且可以通过调节多项参数得到所需的完全禁带;woodpile结构参数调节范围比较宽,为实验制备带来方便.对于不同的三维光子晶体结构,随着介电常数比的增大,完全禁带的宽度和带隙率也会随着增大.还发现了一些以前未引起注意的现象.
关键词:
三维光子晶体
完全禁带
介电常数比
带隙率
平面波展开法 相似文献