共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
3.
Dependence of transmission spectra on director orientation in the photonic crystal with a liquid crystal layer
下载免费PDF全文
![点击此处可从《光电子快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The transmission spectra of one-dimensional(1D) photonic crystals(PCs) with parallel and twisted nematic liquid crystals(LCs) as defect layers are discussed by 4 × 4 matrix method,respectively.The results show that the photonic band gap(PBG) mainly depends on the periodic arrays of dielectric composites.The orientation of director and the symmetry of the director configuration have important influence on the location and amplitude of defect modes.The location and amplitude of defect modes can be controlled conveniently by changing the orientation of director.The symmetry of the director configuration can help us understand the defect modes spectra. 相似文献
4.
新型电磁(光子)晶体贴片天线的研究进展 总被引:8,自引:3,他引:5
介绍了新型电磁(光子)晶体贴片天线的研究进展,尤其是几种新型光子晶体贴片天线。这些光子晶体贴片天线采用基底钻孔、地面腐蚀、加高阻抗表面以及基底上表面腐蚀等方法在贴处天线中加入光子晶体结构,改善了以高介电常数介质为基底的贴片天线的性能,也为贴片天线集成在微波电路上开辟了途径。光子晶体贴片天线这种集低剖面,易集成有好辐射性能于一身的新型天线,必将在移动通信等许多领域发挥作用。 相似文献
5.
The photonic band gap (PBG) structures of four types of annular photonic crystals (PCs) with inner-scatter of rectangular,
square, hexagonal and circle shapes are respectively calculated by the plane wave expansion method. The optimal samples with
the largest gap-midgap ratio for each structure are obtained by scanning the four parameters: filling ratio f, dielectric constant ɛ1, rotating angle θ of inner-scatters and outside radius R of the air ring. The results show that the band gap can be further maximized by adjusting the structural parameters, and
a wide PBG with the gap-midgap ratio of 20.4% is gained in the annular photonic crystal with rectangular inner-scatters. 相似文献
6.
二维复周期光子晶体的带隙结构 总被引:1,自引:0,他引:1
提出了由二维六边形结构和三角结构叠合构成的复周期光子晶体 ,利用平面波展开法计算了由空气中的介质圆柱棒组成的该复周期光子晶体的带结构。结果表明二维六边形结构和三角结构叠合构成的复周期结构的光子晶体可以形成很宽的TE波光子带隙 ,并且具有较宽的TE波和TM波带隙重叠的绝对光子带隙 相似文献
7.
8.
为了获得较大的完全带隙,采用平面波展开法对2维光子晶体的带隙结构进行计算,通过栅格结构连接方形硅介质柱对正方晶格的带隙结构进行优化。在适当调整介质柱宽度和栅格宽度后,所构成的复式结构获得了较大的完全带隙。结果表明,在正方晶格结构的情况下,只有方形硅介质柱且其宽度为0.5a(a为晶格常数)时,仅存在TE模的带隙;只有同周期硅介质栅格结构且栅格宽度为0.22a时,仅存在TM模的带隙;复式结构的情况下,适当调整介质柱宽度w和栅格宽度d,在w=0.5a和d=0.05a时,可以获得较大的完全带隙,其宽度为0.0417ωe(ωe为中心频率);在w不变时,随着d的变化,在0.04a~0.11a出现完全带隙;在d不变时,随着w的变化,在0.42a~0.76a出现完全带隙;在4~36的范围内调整介电常数,在8.41~36之间能够出现不同宽度的完全带隙。这些结果对2维光子晶体的制作和应用是很有帮助的。 相似文献
9.
10.
Photonic crystals (PC) are periodic dielectric structures that, if suitably designed, prohibit light propagation within a frequency band even though the constituent materials may be transparent in this range. One of the remarkable applications of such artificial photonic materials has been to provide guiding of light. Ultimately, to guide light in directions other than straight lines, PC waveguide (PCW) bends are needed, and thus are expected to be essential building blocks of photonic integrated circuits. While bending light through large angles is possible with conventional waveguides, the corner radii of such bends cannot typically be reduced to the electromagnetic wavelength, which hinders the realization of extremely compact devices. And though sharp two-dimensional (2-D) PCW bends have been proposed, the transmission is typically low and/or narrow band. Here we focus on PCWs obtained by introducing line defects in otherwise period 2-D PCs with the aims of enhancing the typical poor and low-bandwidth transmission through tight bends. We show how PCW bends occurring at heterojunctions between different PCs may enable unprecedented flexibility in meeting these aims. The deformation introduced to the usual PC lattice lifted off the angle constraint and resulted in the power transmission greater than 90% over in the 95-nm bandwidth 相似文献
11.
光子晶体是一种周期性电介质材料,具有光子带隙和光子局域等一系列优异的光学特性。制备了多种不同直径的单分散二氧化硅胶体微球,采用垂直沉积法将不同直径,以及同一直径不同浓度的二氧化硅胶体微球自组装成多种光子晶体薄膜,并用扫描电子显微镜和紫外—可见—近红外分光光度计对其微观结构和光学特性进行了表征,结果表明所得晶体薄膜具有三维有序结构,其表面存点、线缺陷。自组装得到的光子晶体薄膜存在明显的光子带隙特征,带隙位置与二氧化硅胶体微球直径有关,带隙中心波长与理论值一致。随着二氧化硅胶体微球浓度的增加,光子带隙深度增加,特性更好,但是,当浓度大于10%时,光子带隙的深度反而减小。 相似文献
12.
13.
二维正方柱结构光子晶体禁带的研究 总被引:2,自引:1,他引:2
利用平面波展开法通过计算机模拟仿真对二维正方排列介质方柱和空气方柱结构以及三角排列介质方柱和空气方柱结构进行了禁带研究。研究发现:这四种二维光子晶体结构都存在完全禁带。介质方柱结构具有较大的TM禁带,而空气方柱结构具有较大的TE禁带。当介质方柱宽度增大时,禁带中心频率均向低频移动,而当空气方柱宽度增加时,禁带中心频率均向高频移动。当增大材料折射率时,禁带中心频率均向低频移动。对于空气方柱结构,应该选取高折射率材料,以提高完全禁带的带隙率。 相似文献
14.
V. G. Golubev D. A. Kurdyukov A. B. Pevtsov A. V. Sel’kin E. B. Shadrin A. V. Il’inskii R. Boeyink 《Semiconductors》2002,36(9):1043-1047
VO2 photonic crystals exhibiting a semiconductor-metal phase transition at 55–75°C have been synthesized by the infiltration of vanadium dioxide (VO2) into opal crystals and the subsequent removal of SiO2 by etching. A study of the optical reflection spectra of such crystals demonstrated that they are characterized by a wide photonic band gap (in the [111] direction of light propagation) in the visible spectral range. The energy position of this band gap changes abruptly upon a phase transition. The temperature shift and hysteresis of the position of the photonic band gap were measured. Quantitative calculations of the reflection spectra of photonic crystals of opal and VO2 were performed in terms of the model of a layered periodic medium, and numerical values of the geometric parameters and optical constants of the studied three-dimensional periodic structures were obtained. 相似文献
15.
The band gap of two-dimensional (2D) photonic crystals with the square lattice of rotational square air columns made of GaAs
and Ge is analyzed by the plane wave expansion method. The effects of dielectric refractive index and crystal structures on
the absolute photonic band gap are investigated. The results show that the maximum absolute photonic band gap emerges when
the square air columns are rotated for 30° and the filling ratio f of the medium is 0.3276. It is also noticed that absolute photonic band gaps appear when the refractive index of the medium
(n) is 2.61. When n=3.70, the width of the absolute photonic bandgaps reaches the maximum. 相似文献
16.
17.
In this paper, an accurate and rapid method is presented to characterize bandgaps of photonic crystals (PCs) constituted by two-dimensional (2D) arrays of dielectric rods with rectangular and circular cross sections. The transmittance and reflectance spectrums of finitely periodic 2D PCs are analyzed using the combination of Rigorous Coupled Wave Analysis (RCWA) and Generalized Scattering Matrix (GSM) methods. In the proposed method, band-edge frequencies of infinitely periodic 2D PCs are determined via Auxiliary Functions of Generalized Scattering Matrix (AFGSM) method using RCWA as a sub-block code. Numerical investigations show that estimating the band-edge frequencies of ideal 2D PCs via AFGSM method is identical with determining the bandgaps of the finite periodic global structure. The high convergence rate of the proposed technique also allows us to perform a bandgap characterization including the higher order Floquet modes without solving the eigenvalue equations for each cascaded layer. Furthermore, the variation of bandgaps when modifying the incidence angle, physical and geometrical parameters are presented for both TE and TM polarizations. The effect of introducing defect in 2D PC structure and resulting band natures are outlined. Our results are in excellent agreement with both theoretical and experimental results in the literature. 相似文献
18.
通过平面波法计算金刚石结构光子晶体的禁带特征,得出:当RA=0.16时,禁带宽度最大;当晶格常数a=8.5mm时,对应的最大禁带宽度为3.5GHz,对应的禁带范围为15.3~18.7GHz.利用CAD软件设计了在x,y,z三个方向上的周期数分别为2,4,6的金刚石结构的光子晶体模型,并采用立体印刷技术制备出了17.4mm×36.54mm× 54.32mm的三维微波金刚石光子晶体.最终通过HP网络测试仪对样品的禁带特征进行测试,结果表明;在晶体的<100》方向上存在频率为14.7~18.5GHz的光子禁带,这与理论值相一致.当电磁波频率为17GHz时,对应的衰减率为-30dB. 相似文献
19.
Sergey L. Prosvirnin Said Zouhdi 《AEUE-International Journal of Electronics and Communications》2001,55(4):260-265
A numerical analysis of reflecting and transmitting properties of multi-layered structures composed of doubly periodic arrays of metallic strips is presented in this paper. Array elements have been selected having the shape of the capital letters C, S and Ω. The metallic strips of arrays are placed on a thin dielectric substrate. These strips may include a concentrated impedance loading. The interferences in the multi-layered array systems, due to multiple reflections of waves between the layers, combined with the resonance properties of single layers lead the structure to acquire typical properties of the photonic band gap (PBG) crystals. 相似文献
20.
为了分析研究1维光子晶体的结构参量对其能带结构的影响,并把这种影响作用应用到滤波器的设计中,采用传输矩阵法、利用MATLAB仿真软件,对不同结构参量的1维光子晶体的能带结构进行了计算仿真,分别得到了不同周期数、不同介质层厚度、不同介质折射率的1维光子晶体的能带分布图,进一步分析比较,得出了1维光子晶体的结构参量对其能带结构的影响。结果表明,较大的周期数可以使1维光子晶体的禁带边缘更加陡峭,通带透射性增强,能带分布更加分明;介质层厚度可以调节光子晶体的能带分布情况及能带宽度;介质折射率比值可以改变禁带宽度,禁带宽度随介质折射率比值的增大而增大。这些结果对宽带带阻滤波器的设计是有帮助的。 相似文献