共查询到20条相似文献,搜索用时 31 毫秒
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光子晶体是由两种或两种以上不同介电常数材料所构成的周期性光学纳米结构.光子晶体结构可分为一维、二维和三维,其中二维光子晶体已成为研究的热点.可调带隙的二维光子晶体可以设计出新型的光学器件,因此,对它的研究具有重要的理论意义和应用价值.本文提出的二维新型函数光子晶体可以实现光子晶体带隙的可调性.所谓二维函数光子晶体,即组成它的介质柱的介电常数是空间坐标的函数,它不同于介电常数为常数的二维常规光子晶体.二维函数光子晶体是通过光折变非线性光学效应或电光效应使介质柱的介电常数成为空间坐标的函数.运用平面波展开法给出了TE和TM波的本征方程,由傅里叶变换得到二维函数光子晶体介电常数ε(r)的傅里叶变换ε(G),其傅里叶变换比常规二维光子晶体的复杂.计算发现当介质柱介电常数为常数时,其傅里叶变换与常规二维光子晶体的相同,因此二维常规光子晶体是二维函数光子晶体的特例.在此基础上具体研究了二维函数光子晶体TE波和TM波的带隙结构,其介质柱介电常数函数形式取为ε(r)=k·r+b,其中k,b为可调的参数.并与二维常规光子晶体TE波和TM波的带隙结构进行了比较,发现二维函数光子晶体与二维常规光子晶体TE波和TM波的带隙结构有明显的区别,二维函数光子晶体的带隙数目、位置以及宽度随参数k的变化而发生改变.从而实现了二维函数光子晶体带隙结构的可调性,为基于二维光子晶体的光学器件的设计提供了新的设计方法和重要的理论依据. 相似文献
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电磁波在周期介质中的传播及二维光子晶体的光子带结构 总被引:5,自引:4,他引:1
光子晶体是光学与凝聚态物理交叉的新领域,也是近年来应用物理学的一个重要研究领域,它是一种由介电常数高的(低的)介质在另一种介电常数低的(高的)背景介质中周期排列所组成的人造多维周期结构材料,能够产生光子带隙。频率落在带隙内的光在晶体里沿任何方向都不能传播,因而具有能够抑制原子、分子的自发辐射等诱人的光电子学特性,在基础研究和实际应用上都有着巨大的潜力。本文在这一领域里进行了富有成效的研究,获得了很好的结果。主要有:(1)利用平面波展开方法来计算二维光子晶体的带隙结构。首先,我们设计正方晶胞的二维光子晶体模型。设x3方向为介质柱的轴方向,二维周期结构在x1-x2平面上。晶胞的晶格常数为a,半径为r,介质柱和空气柱的介电常数分别为εa=17和εb=1,a>2r。设计的核心思想是通过降低光子晶体结构的对称性,消除光子能带在晶体的布里渊区高对称点上的本征简并。(2)对于二维光子晶体的电磁波理论及周期介质中的Bloch波解做了详细的推导,给出了光子晶体中禁带存在的理论依据。同时以正方格子晶格的二维光子晶体为例,验证了电介质在空气圆孔中的排列存在E偏振和H偏振的光子带隙重叠区,称为绝对光子带隙。对于二维的光子晶体,两种本征偏振模式的光子能带结构可以独立地调节,以实现两者的光子带隙的最优重叠, 从而大大提高了二维光子晶体的完全带隙宽度。 相似文献
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提出了一种适用于毫米波及THz波行波放大器的光子晶体栅慢波电路,即横向分布光子晶体栅慢波电路,并提出了分析和设计此类光子晶体栅慢波电路的方法.通过计算光子晶体TE极化的带隙和在带隙内将光子晶体栅慢波电路等效为矩形栅波导慢波电路,从而,光子晶体栅慢波电路的设计得以分为两步独立进行,从而简化了光子晶体栅慢波电路的设计.对横向分布光子晶体栅慢波电路进行了设计和计算,结果表明,与矩形栅波导慢波电路相比,横向分布光子晶体栅慢波电路可以降低工作电压并增加带宽,从而可以降低成本.
关键词:
行波放大器
光子晶体
毫米波
慢波电路 相似文献
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The photonic band gaps in one-dimensional photonic crystals (PCs) are theoretically investigated. A new method to broaden the photonic band gaps is introduced. Based on the similar method, a kind of photonic crystals is constructed to generate photonic band gaps with proportioned central frequencies. This technology can be used for designing nonlinear PCs for harmonic generation. 相似文献
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Oleg L. Berman Vladimir S. Boyko Roman Ya. Kezerashvili Anton A. Kolesnikov Yurii E. Lozovik 《Physics letters. A》2018,382(31):2075-2080
Two-dimensional graphene-based photonic crystal (GPC) formed by a periodic array of the homogeneous dielectric cylinders etched in the alternating graphene and dielectric layers and its inverse counterpart are considered. The transmittance of the photonic crystal is obtained. The waveguide due to the localization of the electromagnetic wave on the lattice defect that breaks the translational symmetry of the GPC of two different topologies is studied. The different topologies of GPC are characterized by different photonic band structures with different widths of photonic band gaps (PBG) and provide different frequencies for the localized electromagnetic wave due to the defect. The frequencies of the localized mode for both type of the GPC, located inside the lowest PBG, are in the range of THz or tens of THz depending on the topology of the GPC. It is shown that the photonic band gap always can be tuned by changing the chemical potential of graphene to provide formation of the localized photonic mode due to the defect. The technological advantages of the GPC, as well as the opportunity to tune the PBG and the frequency of the localized electromagnetic wave in the terahertz region of spectrum for the GPC are discussed. 相似文献
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Zhi-Yuan Li Ben-Yuan Gu Guo-Zhen Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(1):65-73
Two-dimensional (2D) photonic band gaps (PBG) structure fabricated from anisotropic dielectric is studied by solving Maxwell's
equations with use of plane-wave expansion method. Numerical simulations show that absolute photonic band gaps can be substantially
improved in two dimensional square and triangular lattices of cylinders by introducing anisotropy in material dielectricity.
Owing to different refractive indices for electromagnetic waves with E- and H-polarization, the quasi-independent adjustment of band gaps for the E- and H-polarization modes can be implemented by uniaxial crystals with their extraordinary axis parallel to the cylinders. Large
absolute band gaps can be created for uniaxial cylinders in air with a positive anisotropy. In the case of air holes in background
uniaxial dielectric with even a weak negative anisotropy, the absolute band gap can be increased 2-3 times. Large absolute
band gap can also be obtained in other complex configurations of uniaxial and biaxial materials and this enables a full exploitation
of potential utilization for anisotropic materials available in nature. Such a mechanism of band gap adjustment should open
up a new scope for designing band gaps in 2D PBG structures.
Received 26 January 1999 相似文献
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X. Ma 《Applied physics. B, Lasers and optics》2006,84(1-2):339-341
Monodispersed silica microspheres of 270 nm are synthesized by a colloidal solution method. Larger scale perfect three-dimensional
photonic crystals (PCs) are rapidly prepared using the evaporation of acetone to self-assemble the microspheres on quartz
substrates by vertical deposition methods. We find that the pseudo-photonic band gap (PBG) of the PC structure changes with
increasing annealing temperature; it drastically shifts from 450 nm for as-grown crystals to 409 nm for annealing at 800 °C.
CdS photonic crystals are formed by infiltrating CdS nanocrystals of 6 nm into the SiO2 PC structure. The transmission and spontaneous emission characteristics of CdS PCs have been investigated. The clear dip
in the spontaneous emission spectrum relates to the photonic band gap of CdS PCs, indicating that the spontaneous emission
is inhibited in the region of the PBG. The emission band of CdS PCs becomes narrower and sharper than that of CdS nanocrystals;
this demonstrates that the emission band and intensity of the luminescent devices will be tuned by controlling the position
of the PBG.
PACS 42.70.Qs; 42.25.Bs; 78.20.-e; 78.55.Et 相似文献
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H. Xiao D. Z. Yao C. X. Wang S. Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(2):219-229
The absolute photonic band gap (PBG) in two-dimensional (2D) photonic crystal with excentric core-shell rods is studied in
this paper. The core rod shifts away from the core-shell rod center, and its position is decided by two new introduced parameters
— the shift angle θ and the offset ρ. We use the FDTD algorithm to calculate the photonic bands of the photonic crystal, and analyze how the offset and shift
angle affect the photonic bang gap of excentric core-shell photonic crystal for different core rod size. It has been shown
that the variation of the photonic band gap is quite peculiar. 相似文献
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提出了一种新型的非对称性散射体的二维六角晶格光子晶体结构–-太极形介质柱光子晶体. 利用平面波展开法从理论研究这种光子晶体结构的能带特性以及结构参数对完全禁带的影响. 研究表明:散射体对称性的打破, TE模和TM模能带宽度和数目都会有所增加, 有益于获得更宽的完全禁带以及更多条完全禁带.通过参数优化, 发现在ε = 17, R=0.38 μm, r=0.36R, θ = 0° 时, 获得最大完全带隙宽度0.0541(ωa/2πc); 在ε = 16, R=0.44, r=0.2R, θ = 0°时, 光子晶体完全带隙数目最多达到8条.
关键词:
光子晶体
禁带
平面波展开 相似文献
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Jian Shen Shiyang Liu Rong Cao Xin Fan Junjie Du Huaiwu Zhang Zhifang Lin Siu-Tat Chui John Q. Xiao 《Applied Physics A: Materials Science & Processing》2011,105(4):789-793
We experimentally studied magnetically controllable photonic band gaps (PBGs) in two-dimensional magnetic photonic crystals
consisting of ferrite rods. Besides the conventional PBG that relates to Bragg scattering, two other types of PBG, resulting
from magnetic surface plasmon (MSP) resonance and spin-wave resonance, respectively, are observed. The PBG due to MSP resonance
is particularly interesting because of its analogy to surface plasmon in metal; furthermore, it is shown to be completely
tunable by an external static magnetic field from both an experimental and a theoretical point of view. 相似文献
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Here we demonstrate a novel quantitative procedure to pursue statistical studies on the geometric properties of photonic crystals and photonic quasicrystals (PQCs) which consist of separate dielectric particles. The geometric properties are quantified and correlated to the size of the photonic band gap (PBG) for wide permittivity range using three characteristic parameters: shape anisotropy, size distribution, and feature-feature distribution. Our concept brings statistical analysis to the photonic crystal research and offers the possibility to predict the PBG from a morphological analysis. 相似文献
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Akimov AV Tanaka Y Pevtsov AB Kaplan SF Golubev VG Tamura S Yakovlev DR Bayer M 《Physical review letters》2008,101(3):033902
The elastic coupling between the a-SiO2 spheres composing opal films brings forth three-dimensional periodic structures which besides a photonic stop band are predicted to also exhibit complete phononic band gaps. The influence of elastic crystal vibrations on the photonic band structure has been studied by injection of coherent hypersonic wave packets generated in a metal transducer by subpicosecond laser pulses. These studies show that light with energies close to the photonic band gap can be efficiently modulated by hypersonic waves. 相似文献
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The effects of the defect and doping on the transmission properties are investigated in two-dimensional photonic crystal (PC) with triangular rods using the finite difference time domain (FDTD) method. The results show that the width and the central position of the photonic band gap (PBG) depend on the thickness of rods with defect or composite-defect, and the refractive index of doped dielectric rods. The transmission properties of composite-defect combined with doping are further investigated. The thinner the nested concentric triangular rod and the smaller the refractive index is, the wider the band gaps is. 相似文献
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Self-imaging effect in photonic crystal multimode waveguides exhibiting no band gaps 总被引:1,自引:0,他引:1
The properties of the propagating field in multimode photonic crystal waveguides (PCWs) exhibiting no photonic band gaps (PBGs) are investigated. The transmission spectrum shows that the input field can be guided with high efficiency, and resemble index-guided modes owing to the combination of total internal reflection (TIR) and distributed Bragg reflection (DBR). Self-imaging effect happens and the filling fraction determines the beating lengths. The rows of air holes decide DBR coming from the mirrors on both sides of the guiding region, which governs the transmission spectrum. It provides a new way to realize the components for both polarizations by combining PBG and TIR effects in PCWs. 相似文献
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High quality photonic crystal heterostructures with a thin titania planar defect layer between its two constitutional photonic crystals were fabricated and their structural and optical properties were analyzed. The results suggest that the thin planar defect layer is beneficial to separate the two constitutional photonic crystals from each other and to reduce the roughness of the interface. The quality of the resulting photonic crystal heterostructures is improved largely and the main features of the photonic band gaps of the two constitutional photonic crystals are inherited. The predominant optical quality of these heterostructures (e.g. deep double photonic band gaps and steep photonic band edges) may afford new flexibility and functionality for engineered photonic behavior in practical devices such as late-model light-operated switches. 相似文献
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The band structure of a two-dimensional superconducting photonic crystal is studied. The temperature dependence of the photonic band structure in a wide temperature region below the superconducting transition is analyzed. It is found that the photonic crystal has two full band gaps and two incomplete band gaps, which are shifted to the high frequency region with decreasing temperature. 相似文献