首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 125 毫秒
1.
利用平面波展开方法计算了波状结构二维光子晶体(2DPC)的等频面,对等频面内矩形轮廓的等频线进行研究,提出了波状结构2DPC的自准直特性,运用时域有限差分(FDTD)方法模拟了波状结构2DPC在不同入射角情况下对所入射高斯光束的自准直作用.将波状结构2DPC的自准直特性运用到近场亚波长成像,模拟了波状结构2DPC的自准直亚波长成像效果,单光源的成像分辨率达到0.28λ,且随着光源逐渐远离近场范围而降低. 关键词: 光子晶体 自准直 等频面 亚波长成像  相似文献   

2.
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   

3.
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   

4.
童元伟  田双  庄松林 《物理学报》2011,60(5):54201-054201
本文采用硅柱子周期性排列构成六角结构光子晶体,用平面波展开方法和FDTD方法研究表明,此结构光子晶体存在等效折射率接近-1的频率区域.在等效折射率趋于-1但不等于-1时,此光子晶体平板结构超透镜能形成一个非近场的像.模拟还发现,此结构平板光子晶体等效折射率为非-1时,可以亚波长成像. 关键词: 负折射 光子晶体 亚波长 成像  相似文献   

5.
填充率渐变型波状结构二维光子晶体   总被引:6,自引:2,他引:4  
填充率渐变引起的能带结构和等频面结构的变化是填充率渐变型波状结构二维(2D)光子晶体(PC)产生光路转弯现象的根本原因,由于TM模和TE模在能带结构上存在差异,光路转弯现象就具有明显的偏振选择特性,能够实现归一化频率a/λ为0.29~0.33的偏振分束。利用时域有限差分(FDTD)法模拟了TM模的U型转弯波导,发现出射光位置对入射波长和入射角的变化很敏感,位移变化量分别达到0.38μm/10 nm和0.29μm/(°)。利用TM模的U型转弯波导构建了新型的平行平面谐振腔,并指出由填充率渐变型波状结构二维光子晶体和一维多层薄膜构成的混合结构在光分束和抑制光束发散方面的作用及其在平行平面谐振腔中的潜在应用。  相似文献   

6.
童元伟  毛宇  庄松林 《物理学报》2010,59(8):5553-5558
利用电介质材料周期性排列构成二维六角结构光子晶体,用平面波展开法研究了二维光子晶体材料各个能级的等频率曲线图,发现此结构光子晶体在多个频段上存在负折射特性,用时域有限差分(finite difference time domain,FDTD) 数值计算模拟也得到了相同的结果. 关键词: 光子晶体 左手化媒质 负折射 多频段  相似文献   

7.
毛宇  童元伟 《光子学报》2014,39(9):1562-1566
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   

8.
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   

9.
张波  王智 《物理学报》2007,56(3):1404-1408
提出并优化了由单排渐变介质波导构成的二维空气孔型光子晶体负折射平板透镜表面的减反层,改善了成像质量.二维时域有限差分模拟计算结果表明,采用减反层后,在入射角小于23°的范围内,在使得有效折射率neff=-1的工作频率处,光子晶体表面对从空气一侧入射的平面波的反射率可降低到1%以下. 关键词: 光子晶体 负折射 平板透镜 减反层  相似文献   

10.
为了研究光子晶体中的负折射行为,我们应用2维TM模时域有限差分方法,数值模拟了高斯波束从自由空间垂直入射和斜入射到二维三角晶格光子晶体平板后的折射现象,并给出了平板内外的电场强度分布.模拟结果显示:垂直入射时,光子晶体平板对高斯波束具有汇聚作用,汇聚特性随着波源到晶体的距离的改变而发生显著的变化;斜入射时,折射波束与入射波束也均在法线的同一侧.结果证明了高斯波束在光子晶体和空气的交界面发生了负折射.模拟结果有望在制作聚焦透镜、带通滤波器、耦合器等光子晶体器件方面得到重要应用.  相似文献   

11.
We experimentally demonstrate subwavelength resolution imaging at microwave frequencies by a three-dimensional (3D) photonic-crystal flat lens using full 3D negative refraction. The photonic crystal was fabricated in a layer-by-layer process. A subwavelength pinhole source and a dipole detector were employed for the measurement. By point-by-point scanning, we obtained the image of the pinhole source shown in both amplitude and phase, which demonstrated the imaging mechanism and subwavelength feature size in all three dimensions. An image of two pinhole sources with subwavelength spacing showed two resolved spots, which further verified subwavelength resolution.  相似文献   

12.
Yuntuan Fang  Tinggen Shen 《Optik》2007,118(2):100-102
Diverse imaging of point source by a two-dimensional photonic crystal slab with square lattice is studied by the finite-difference time-domain method. Given proper frequencies, there seems to be some special directions like channels guiding the light propagation inside the photonic crystal, along which some images will be created. It is suggest that except negative refraction there should be other mechanisms making point image by two dimensional photonic crystal slab.  相似文献   

13.
The problem of subwavelength imaging via a photonic crystal slab lens made of two-dimensional (2D) square arrays of parallel dielectric cylinders in air is studied and discussed theoretically. The finite-difference time-domain method is employed to investigate the unique features of imaging by such lens. We confirm earlier findings that a photonic crystal slab lens can provide the imaging of a point source. By analysing the transmission properties of the proposed structure, we demonstrate that inside the all-angle negative refraction, there are some favourable directions for waves to travel. We show that the surface termination of the photonic crystal is a key parameter to obtain a good quality image. The super-resolution of two sources separated by a distance less than the wavelength is also considered. It is shown that the achievable resolution is limited by the slab length.  相似文献   

14.
We experimentally and theoretically demonstrate single-beam negative refraction and superlensing in the valence band of a two-dimensional photonic crystal operating in the microwave regime. By measuring the refracted electromagnetic waves from a slab shaped photonic crystal, we find a refractive index of -1.94 that is very close to the theoretical value of -2.06. A scanning transmission measurement technique is used to measure the spatial power distribution of the focused electromagnetic waves that radiate from a point source. The full width at half maximum of the focused beam is measured to be 0.21 lambda, which is in good agreement with the finite difference time domain method simulations. We also report a subwavelength resolution for the image of two incoherent point sources, which are separated by a distance of lambda/3.  相似文献   

15.
仲义  许吉  陆云清  王敏娟  王瑾 《物理学报》2014,63(23):237801-237801
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   

16.
Negative refraction and subwavelength imaging properties of a two-dimensional (2D) photonic crystal (PC) slab are studied by the finite-difference time-domain method. The PC consists of a triangular lattice of air holes immersed in a dielectric. For a certain frequency range in the third photonic band, the directions of the group velocities and the phase velocities can be opposite, so the PC can work as a kind of negative refractive-index material. The light radiated from a point source can form a subwavelength image spot through the PC slab. Negative refraction and an effective refractive index of the PC slab n = -1 can be achieved for the incident wave with its incident angle within a certain range.  相似文献   

17.
High-index contrast photonic crystals possess an intricate photonic band structure that is responsible for surprising phenomena as the surperprism effect, self-collimation, power splitting or negative refraction. Recently, it was reported that at the interface between an isotropic medium and a uniaxial crystal (or between two uniaxial crystals) a phenomenon known as amphoteric refraction, that is, positive as well as negative refraction, can take place. By means of a equifrequency contours analysis and finite-difference time-domain simulations, we show that a two dimensional photonic crystal can also present amphoteric refraction by properly choosing the lattice orientation and the termination. However, total transmission is difficult to achieve because a Bloch mode is excited inside the photonic crystal and the coupling efficiency from this mode to an external plane wave is lower than one.  相似文献   

18.
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   

19.
We report our experimental results on two-dimensional left-handed metamaterials (LHM) exhibiting negative refraction and subwavelength imaging. Transmission and reflection spectra of LHM are studied and a left-handed transmission band is observed at the frequencies where both dielectric permittivity and magnetic permeability are negative. Impedance matching is verified both with the experiments and simulations. The two-dimensional LHM structure is verified to have a negative refractive index. We employed three different methods to observe negative refraction; refraction through prism-shaped LHM, beam shifting method, and phase shift experiments. We further demonstrated subwavelength imaging and resolution using LHM superlenses. The effect of thickness on the resolving power is investigated experimentally.  相似文献   

20.
We report on the first experimental evidence of negative refraction at telecommunication wavelengths by a two-dimensional photonic crystal field. Samples were fabricated by chemically assisted ion beam etching in the InP-based low-index constrast system. Experiments of beam imaging and light collection show light focusing by the photonic crystal field. Finite-difference time-domain simulations confirm that the observed focusing is due to negative refraction in the photonic crystal area.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号