共查询到19条相似文献,搜索用时 62 毫秒
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采用平面波展开法和时域有限差分法研究了由空气环组成的二维三角晶格光子晶体平板的负折射成像特性.研究结果表明对于外半径为 0.4 a,内半径 0—0.13a的空气环型光子晶体,第二能带中归一化频率为 0.3 的电磁波可以实现有效折射率为-1的负折射成像.通过光子晶体有效折射率的计算,得到了有效折射率为-1的电磁波频率随空气环内径由0—0.2 a变化的规律,并由对应等频曲线的变化解释了结构参数对光子晶体平板成像的影响.
关键词:
光子晶体
空气环
负折射
等频曲线 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
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准周期光子晶体平板透镜的光会聚 总被引:2,自引:1,他引:1
提出了一种能够实现负折射的准周期光子晶体(QPC).该准晶光子晶体具有十二重对称性,由介质背景下空气孔的准周期阵列组成.用时域有限差分方法研究了电磁波通过该十二重准品后的传播行为.对劈形准品样品的研究表明,电磁波在该准晶结构中发生了负折射现象.进一步利用该准晶制成平行平板,研究了平板的表面截面对电磁波传播的影响.发现改变平板的表面截面,可以调节电磁场在板后的分布.在合适的界面条件下,准晶平板对电磁波实现了会聚.因此,在实际应用中应仔细选择适当的界面参数. 相似文献
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利用二维光子晶体的等频线分析原理和平面波展开方法,得到了使二维光子晶体产生全入射角负折射(All-Angle Negative Refraction,AANR)现象时,入射电磁波的频率取值范围.同时,分析了AANR频率范围随着结构参量(晶格类型、介质棒半径与晶格周期的比值)和电磁参量(介质柱介电常量、本底介电常量、入射电磁波偏振方向)变化的行为.结果表明:固定组成光子晶体的一种介质的介电常量,另一介质的介电常量只有达到一定阈值,才有可能使光子晶体出现AANR现象.在给定两种介质介电常量的条件下,存在使AANR频率范围最大化的结构参量和电磁参量. 相似文献
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以砷化镓圆形介质柱在空气中构成二维六边形排列结构的光子晶体为例,利用时域有限差分法模拟研究了光子晶体表面结构改变对负折射透射光强的影响.模拟结果表明:针对同一结构光子晶体,在可产生负折射现象的入射光频率范围,改变光子晶体表面两侧圆形介质柱的半径和顺向侧移两侧表面最外层圆形介质柱都会均对负折射透射光强产生影响. 相似文献
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Existing conditions of full bandgaps and absolute negative refraction in metallic-dielectric photonic crystal 总被引:1,自引:0,他引:1 下载免费PDF全文
This paper has theoretically studied the characteristic frequencies
of band structures in two-dimensional metallic-dielectric photonic
crystals. It is demonstrated that a large filling fraction benefits
the existence of absolute photonic band gap, while a smaller filling
fraction benefits an absolute negative refraction band. In addition,
it also finds that the relation between the cut-off frequency of
E-polarized wave and the filling fraction exceeding 10{\%} is content
with a linear increasing function, whose coefficients are exponential
to the normalized lattice constant. These investigations have
significant implications for tuning the operational frequencies to
desired applications and manufacturing photonic crystals. 相似文献
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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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N. Fabre S. Fasquel C. Legrand X. Mélique M. Muller M. François O. Vanbésien D. Lippens 《Opto-Electronics Review》2006,14(3):225-232
We report on the numerical simulation and fabrication of a two-dimensional flat lens based on negative refraction in photonic
crystals. The slab acting as a lens is made of an hole array (operating at the wavelength of 1.5 μm) etched in a InP/InGaAsP/InP
semiconductor layer. We first study the key issues for the achievement of a negative refractive index taking advantage of
folding of dispersion branches with main emphasis in dispersion properties rather than the opening of forbidden gaps. The
diffraction and refraction regimes are analysed according to the comparison of the wave-vector with respect to the relevant
dimensions of the hole array. In the second stage, we illustrate technological challenges in terms of e-beam lithography on
a sub-micron scale and deep reactive ion etching for an indium phosphide based technology. 相似文献
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柱矢量光束具有柱对称性的偏振分布,其独特的光场分布和聚焦特性被广泛应用于光学微操纵及光学成像等领域,并迅速向亚波长尺度拓展.通常,亚波长尺度聚焦采用等离激元透镜实现,但存在光场调控的偏振态局限性.而借助光子晶体的负折射效应,不仅能够实现亚波长聚焦或成像,而且应对正交偏振态同时有效.采用对电磁波具有更强调控能力的一维金属光子晶体结构,计算得到的能带结构和等频曲线表明其负折射效应在特定波段对正交偏振态同时有效.在此基础上设计出一维金属光子晶体柱对称平凹镜结构,通过有限元算法模拟显示了可见光波段的径向和旋向偏振光的同时亚波长聚焦行为.进一步的结果表明,改变柱矢量光束的偏振组分能够直接有效地调节焦场空间分布及偏振分布特性.所提出的平凹镜结构能够实现对任意偏振组分的柱矢量光束的亚波长尺度聚焦,且该结构的设计对于各波段情况均有参考意义.该研究结果对小尺度粒子的光学微操纵、超分辨率成像等相关领域具有潜在的应用价值. 相似文献
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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
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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