共查询到20条相似文献,搜索用时 161 毫秒
1.
运用直线法对含有不同参数支撑介质的平面型电磁带隙(EBG)结构进行了分析.概述了算法的实现过程,使用周期边界条件隔离出一个结构单元作为计算区域,并利用直线法得到了位函数在各层介质界面间的传输方程.通过联立场分量与位函数的变换关系和界面处切向场分量的连续性条件,建立了本征方程, 得到了表征该EBG 结构表面波带隙的本征模频带图.同时,使用该方法对含有不同介电常数、不同厚度支撑介质的表面波带隙进行了计算.通过对计算结果的分析,得到了支撑介质对平面型EBG 结构带隙特性影响的六条结论,为平面型EBG 结构的设计
关键词:
超媒质
光子带隙
周期结构
表面波 相似文献
2.
利用二维三角格子金属光子带隙谐振腔代替回旋管的传统柱形谐振腔,并对腔体进行了TE波模式的计算与分析.综合考虑腔体内外的结构特征,给出了光子带隙谐振腔冷腔模式理论的研究方法,发现腔内存在单模工作的可能与条件以及非角对称情况下的电磁模式分布特征.研究结果表明,利用光子带隙谐振腔代替回旋管的传统腔体,可使回旋管在不受腔体横向尺度限制的条件下实现单模工作.这对于提高回旋管的功率容量、有效实现高次单模与高次回旋谐波耦合条件下的注-波互作用、降低工作磁场并从物理上根本改变回旋管的工作状态提供了理论依据.
关键词:
回旋管
金属光子带隙
谐振腔 相似文献
3.
为解决准横电磁(TEM)模波导工作带宽较窄的问题,提出采用金属贴片电磁带隙(EBG)结构在金属波导中创建准TEM波.通过理论分析和数值计算,研究金属贴片EBG结构创建准TEM波导对展宽带宽、改善传输特性和增强准TEM波电场分布均匀性的作用.模拟结果表明,在频率14 GHz附近,金属贴片EBG将TE10模成功转换成准TEM模,转换带宽达到1.7 GHz,且在波导横截面83.9%的面积上电场分布均匀性达到84.7%.
关键词:
电磁带隙
金属贴片电磁带隙结构
磁导体
准横电磁模波导 相似文献
4.
5.
把具有宽完全带隙的粗锐复合的周期常数为a的二维正方格子再与周期常数为a2的大周期简单正方格子复合,发现大周期正方格子起缺陷作用.并发现当a2<5a时,缺陷态明显地随入射角度变化.此变化随a2的增大而减少.用FDTD方法计算了其透射和反射谱,结果表明缺陷峰透射率与a2的大小成反比.另外还发现: 缺陷峰结构与大周期正方格子的圆柱直径的关系曲线与a2关系不大.通过调节大周期正方格子的圆柱的直径,可获得单
关键词:
光子晶体
光子能隙
复式结构
缺陷态 相似文献
6.
7.
为了减弱大气摩擦引起的高温损伤,航空飞行器雷达天线一般都会加装天线罩或介质窗,将电磁带隙(EBG)结构的禁带特性和阶梯型微带天线的带宽及良好的匹配特性相结合,设计了一种含介质窗的EBG结构阶梯型微带天线,并计算分析了天线的辐射特性及介质窗对辐射特性的影响。结果表明:EBG结构产生的带隙能够制约天线表面波的传播,改善天线的带宽和增益性能,且当介质窗存在时,该结构亦可降低天线与介质窗间的互耦效应。这为含介质窗的EBG结构阶梯型微带天线的设计和应用提供了一定理论参考。 相似文献
8.
为了利用在声学领域极具应用前景的双锥型五模式超材料进行隔声降噪,提出一种双锥宽直径不全同型五模式超材料.利用有限元方法分析了其声子能带结构、各波模相速度、品质因数随结构与材料参数的变化关系,在实用性和稳定性上与窄直径不同型五模式超材料作了比较.宽直径不全同型五模式超材料在保持原始五模式结构单模传输能带的前提下,还产生了更低频、宽带的三维完全带隙,且结构更稳定,重量更轻。双锥型五模式超材料在特定宽直径不同时具有三维完全带隙,品质因数主要由结构参数决定,各材料参数只是不同程度地影响带隙的绝对宽度和位置.研究结果表明双锥宽直径不全同型五模式超材料有望用于带隙调控和隔声。 相似文献
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11.
设计了一种新型矩形点阵光子晶体光纤,该光纤纤芯缺失一根空气柱,包层沿光纤长度方向在普通矩形点阵光子晶体光纤中每两列之间隔一行插入一列空气孔而形成正方形网孔结构.采用全矢量有限元法并结合各向异性完美匹配边界条件,对该光纤的色散、双折射和约束损耗进行了数值模拟.结果发现,该光纤具有高双折射负色散效应和较强的模约束能力,约束损耗小于10-2dB·m-1,通过改变光纤结构参数(即空气孔间隔Λ和相对孔间隔d/Λ),可以调节该光纤高双折射负色散工作波长.若调整光纤结构参数Λ=2.0μm,d/Λ=0.4,该光纤在C波段(1.53—1.565μm)呈现负色散并具有负色散斜率,双折射高达10-2,非线性系数接近55km-1W-1.该光纤将在保偏光通信、色散补偿以及基于四波混频的波长转换器设计等方面具有重要的应用. 相似文献
12.
《Physics letters. A》2003,307(4):196-201
An open Λ-type three-level atom in a photonic crystal can become nearly transparent to a resonant probe field even if the density of modes (DOM) has no mathematical singularity. A high-Q defect mode can induce perfect coherent population trapping. The role of singularity/smoothness of DOM is analyzed. 相似文献
13.
Single axial mode operation (<200 MHz optical bandwidth) of a high repetition rate periodically poled lithium niobate optical
parametric oscillator (OPO) has been obtained at signal wavelengths between 1.46 μm and 1.64 μm. OPO signal slope efficiencies
of 35% have been measured for repetition rates of 5–20 kHz. Single mode operation required spectral narrowing of both the
pump laser and the OPO. A simple technique of prelase Q-switching was implemented to reduce the optical bandwidth of the cw diode-pumped Nd:YAG pump laser to <1 GHz. A single intracavity
étalon was then sufficient to ensure single frequency oscillation of the OPO signal. The OPO output was stable with a smooth
spatial profile and an M
2 value of 1.3.
Received: 29 September 1999 / Published online: 27 January 2000 相似文献
14.
A. H. Gevorgyan 《Optics and Spectroscopy》2009,106(1):43-49
The specific features of defect modes of chiral photonic crystals with an anisotropic defect have been investigated. Peculiarities of the spectra of polarization observables of the system under consideration are analyzed at different thicknesses of the defect layer. It is shown that single refraction occurs in a defect mode, even though the system is anisotropic and inhomogeneous. We also investigated the specific features of the spectra of the photon density of states, light intensity at the defect center, and the Q factor of defect modes at different thicknesses of the defect layer and chiral photonic crystals. It is shown that the lasing wavelength of chiral photonic crystals with an anisotropic defect enriched in laser dyes (resonant atoms) can be controlled in a different way: by varying the defect layer thickness. It is shown that this system can operate as a narrow-band filter (mirror) with a controlled frequency width and location of the total transmission (reflection) range on the frequency scale. 相似文献
15.
Effect of interstitial air holes on Bragg gratings in photonic crystal fibre with a Ge-doped core 下载免费PDF全文
The effect of interstitial air holes on Bragg gratings in photonic
crystal fibre (PCF) with a Ge-doped core is numerically investigated
by using the beam propagation method (BPM). It is shown that the
interstitial air holes (IAHs) can make Bragg resonance wavelength
λB shift a little towards short wavelengths and
increase λB-λ1 (the wavelength spacing
between the main peak with Bragg resonance wavelength λB and the first side peak with wavelength λ1 and the
coupling coefficient к of Bragg resonance. Moreover, when
the ratio of air hole diameter (d) to pitch (Λ),
d/Λ, is small, IAHs can suppress the cladding mode
resonance. When d/Λ is large, IAHs increase the number
of mode that could strongly interact with the fundamental mode. By
comparing the transmission spectral characteristics of PCF-based
fibre Bragg grating (FBG) with IAHs with those without IAHs at the
same air-filling fraction, it is clarified that the change of
transmission spectral characteristics of PCF-based FBG with IAHs is
not due to a simple change in air-filling fraction. It is also
closely related to the distribution of interstitial air holes. 相似文献
16.
Nuclear shadowing corrections are known to be dominated by soft interactions. They grow as function of 1/x more slowly than the single scattering term, which has an essential contribution from hard interactions. Therefore, we predict
that nuclear shadowing vanishes eventually at very lowx, provided thatQ
2 is high and fixed. At the same time, at medium and lowQ
2, nuclear shadowing grows with 1/x. Our formalism nicely explains also the recent NMC data onQ
2-dependence of the nuclear shadowing. The effect of gluon fusion is found to be of little importance for the nuclear structure
function in the available range ofx.
Communicated by W. Weise 相似文献
17.
Wenyuan Rao 《Optik》2010,121(21):1934-1936
We present a design of all-optical switches based on one-dimensional photonic crystals (1D PhC) doped with nonlinear optical materials. The 1D PhC switch structure is composed of a PhC cavity sandwiched by two accessional PhC microcavities. The center PhC cavity has two resonant frequencies with nearly the same quality factors (Q), while the accessional PhC cavities have the same resonant frequency, which is equal to one of the resonant frequencies of the center cavity. The two accessional PhC cavities cause reduction of Q value in this resonant frequency and result in different Q values of two modes. We realize all-optical switch effect by selecting pump light wavelength at the low Q mode and probe light wavelength at the other mode. The theoretical simulations by using the finite difference time domain method show that the pump light intensity required to realize optical switch effect in the designed switch is 50 times smaller than that in one-dimensional photonic crystals cavity with only one resonant mode. 相似文献
18.
W. Melnitchouk 《The European Physical Journal A - Hadrons and Nuclei》2003,17(2):223-234
We explore the relationship between exclusive and inclusive electromagnetic scattering from the pion, focusing on the transition
region at intermediate Q2. Combining Drell-Yan data on the leading twist quark distribution in the pion with a model for the resonance region at large
x, we calculate QCD moments of the pion structure function over a range of Q2, and quantify the role of higher twist corrections. Using a parameterization of the pion elastic form factor and phenomenological
models for the π↦ρ transition form factor, we further test the extent to which local duality may be valid for the pion.
Received: 10 February 2003 / Accepted: 12 March 2003 / Published online: 27 May 2003 相似文献
19.
Specific features of the defect modes of cholesteric liquid crystals (CLCs) with an isotropic defect, as well as their photonic
density of states, Q factor, and emission, have been investigated. The effect of the thicknesses of the defect layer and the system as a whole,
the position of the defect layer, and the dielectric boundaries on the features of the defect modes have been analyzed. It
is shown that when the CLC layer is thin the density of states and emission intensity are maximum for the defect mode, whereas
when the CLC layer is thick, these peaks are observed at the edges of the photonic band gap. Similarly, when the gain is low,
the density of states and emission intensity are maximum for the defect mode, whereas at high gains these peaks are also observed
at the edges of the photonic band gap. The possibilities of low-threshold lasing and obtaining high-Q microcavities have been investigated. 相似文献
20.
E. Lotfi K. Jamshidi-Ghaleh F. Moslem H. Masalehdan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,60(2):369-372
The photonic band-gap of the two kinds of 1D photonic crystal structure
which is composed of the form of (AB)
N1
C
m
(BA)
N2
, one with a
metamaterial defect layer (MDL) and the other one with a dielectric defect
layer (DDL) are studied. Our results show that in both cases, where there is
only one defect layer, m=1, no defect mode exists, but for two defect
layers (m=2) there is a single defect mode which is centered in the middle
of the band-gap. The width of the defect mode in DDL is narrower than that
in MDL. For a number of defects of more than two (m>2) and even, in both of
the MDL and DDL structures, there is only one defect mode. For m>2 and
odd, the defect mode in the MDL vanishes, but for DDL there is two defect-mode symmetrically centered in the middle of the
band-gap. The effects of the
defect layers refractive index value, the periodicity number of the
structures and the incident angle on the properties of the defect modes and
the transmittance spectrum are discussed. 相似文献