共查询到20条相似文献,搜索用时 31 毫秒
1.
研究了横磁波在各向同性右手介质和双曲色散型单轴左手介质界面处波矢和能流的折射。计算发现,当入射角在很大范围内变化时,波矢的折射角和能流的折射角几乎不变。调节光轴角可使波矢折射角和能流折射角随入射角变化不敏感的现象更明显,经分析计算给出光轴角的调节范围。这一现象是由双曲色散型单轴左手介质的各向异性及负的主折射率引起的,可以用来实现光束准直、光束整合、光束压缩以及方便的光束耦合。如果光从双曲色散型单轴左手介质向各向同性右手介质入射,还能实现超棱镜(superprism)现象。计算了横磁波穿越界面时的透过率,证实双曲色散型单轴左手介质可能实现上述应用。 相似文献
2.
We report on the negative refraction and left-handed behavior of two-dimensional photonic crystals. For the triangular two-dimensional photonic crystals there are two saddle points and a key point in the first Brillouin zone for the second band, which play important role to determine the refraction phenomena. There is no determined relation between the left-handed behavior and the negative refraction. The refraction phenomena depend on the band structure and the configuration of the incident light. For the first configuration, the first Brillouin zone can be divided into three parts. In part I there are negative refraction and left-handed behaviors. In part II there are normal refraction and left-handed behaviors. In part III there are normal refraction and right-handed behaviors. For the second configuration, the first Brillouin zone can only be divided into two parts. For these complex refraction phenomena, it is meaningless to define the phase refractive index, and it is necessary to define the effective refraction index by a Snell-like formula, and the value of the effective index is determined by the configuration and the band structure. 相似文献
3.
基于裂缝谐振环结构的降频技术,首先设计了一种电尺寸较小的左手介质微带线单元,并根据电磁波在微带线上的传输和反射数据,分别计算了左手介质的有效介电常数和有效磁导率.之后针对左手介质八元阵列进行三维电磁仿真实验,结果表明该八元阵列在左手介质频段上具有独特的后向波效应,从而证实了该左手介质频段的存在.与传统的左手介质微带单元相比,阐述的左手介质单元的电尺寸减小了60%,而且结构简单,便于加工,适用于平面电路器件的小型化等应用研究工作.
关键词:
左手介质
小型化
双负特性
后向波特性 相似文献
4.
提出了基于传输线比拟模型的左手材料微结构设计方法,并对此进行了分析、验证.首先根据已有的具有左右手性质的基本传输线模型,通过类比构建了具有左手性质的新模型,进而通过定性分析传输线网络中的各元件与微结构连续介质构型的形状及尺寸的对应关系,推断出模型中各部分的具体尺寸,从而得到了一个合理的左手材料微结构构型及其对应的传输线比拟模型.对设计的模型进行了实验测试,验证了模型确实具有左手性质.最后,通过数值模拟和实验,研究了微结构的各个尺寸参数对材料出现左手性质的带宽和频段的影响,确定了微结构中对左手性质影响最大的尺寸参数. 相似文献
5.
Monika Rajput 《Optik》2011,122(16):1412-1417
A new left-handed isotropic design of semiconductor Photonic Crystal with plasmonic (Aluminum) nanorod inclusion is analyzed and proposed to demonstrate All-Angle Negative Refraction (AANR) with blue light amplification. It is shown that the proposed structure provides negative real values of both permeability (μ) and permittivity (?) with extremely low imaginary values for visible light. Phase slope and phase velocity is shown to be negative for blue light for proposed left-handed structure. Index matched to the incident medium and compensated losses due the gain assistance lead the light amplification in the designed structure. Finite Difference Time Domain (FDTD) method is applied to study left-handed transmission and reflection properties. Extremely high Left-Handed Transmission Efficiency is calculated which is found to be more than 99% for the proposed structure. Fabrication tolerance with effect of change in plasmonic nanorod radius by ±10% is also analyzed. Further, left-handed transmission for blue light is confirmed by analyzing the far-field spectrums of the proposed structure obtained by employing 3D FDTD method. Demonstration and study of near-field and far-field resonance reveals the nano-photonic application potential of the proposed structure as directional optical nano-antenna, polarizer and filter. 相似文献
6.
Qingfeng Zhang Shanjia Xu 《International Journal of Infrared and Millimeter Waves》2006,27(11):1539-1552
A novel uniplanar 2-D composite right/left-handed transmission line (CRLH-TL) structure is proposed based on a general transmission
line theory and the way to increase the relative operating bandwidth in the left-handed (LH) region and lower the LH operating
frequency is illustrated. In addition, a new method to extract parameters and calculate the Bloch impedance of the structure
is presented. Numerical results of the dispersion as well as the extracted parameters are given, which are calculated based
on full-wave simulation. The present 2-D uniplanar CRLH-TL structure is applicable to 2-D left-handed materials in lower and
wider LH frequency range.
Supported by the National Natural Science Foundation of China (No. 60371010) (No. 60471037) (No. 63531020) 相似文献
7.
8.
Tunable Effect of Double-Connective Dendritic Left-Handed Metamaterials Based on Electrorheological Fluids 下载免费PDF全文
We present double-connective dendritic unit pairs which exhibit the left-handed property for electromagnetic wave normal incidence. Based on the tunable characteristics of electrorheological fluids (ERF) as the electric field, we experimentally study the influence of the distance of electrodes, the number of stacked layers, and the intensity of the external electric field upon the ERF to the left-handed transmission peak of the double-connective dendritic structure. The results show that the transmission could be enhanced with the increase of distance or the number of layers. Furthermore, by changing the intensity of the electric fields, the left-handed transmission peak can be modulated actively, and the maximum shift is up to 160 MHz. 相似文献
9.
Fan-Yi Meng Kuang Zhang Fang Zhang Qun Wu Jong-Chul Lee 《Applied Physics A: Materials Science & Processing》2011,102(3):509-515
The design and characterization is described of a reconfigurable subwavelength waveguide based on magnetic metamaterial. The
waveguide is capable of reconfiguring its propagating mode from right-handed to left-handed, which can be applied in the design
of novel microwave and RF devices such as leaky wave antennas with broadened scanning range. The waveguide consists of a rectangular
metallic waveguide loaded by two pieces of different magnetic metamaterials, which are structured by the same cells—modified
split ring resonators (MSRRs)—with different arrangements. Positions of the two pieces of metamaterials in the waveguide can
be reconfigured separately by the control mechanism. The simulated transmission data show that the waveguide has a passband
below the cutoff frequency of the hollow waveguide either in the left-handed case or in the right-handed case. The extracted
constitutive parameters have demonstrated that the effective permittivity and permeability of the waveguide are simultaneously
negative in the left-handed case and positive in the right-handed case. The magnetic field and surface current distributions
in the waveguide confirm that the waveguide operates as can be expected. The influence of the control mechanism on the performance
of the waveguide is studied. It is shown that the influence is so minor that it can be neglected. 相似文献
10.
In this paper, we suggest a possibility of providing left-handed
material with parallel ferromagnetic nanowires electrodeposited into an insulating
polycarbonate membrane. We find that such a composite shows left-handed
properties when the damping factor α satisfies α<αc, where αc is the
critical damping factor which is affected by the filling factor of ferromagnetic
nanowires. We also investigate the magneto-optical properties of such a
composite and find that at the frequency region where the composite
exhibits left-handed property, both the Faraday rotation angle and ellipticity
of the film show obvious change apart from a jump in transmission coefficient
at the frequency region near the ferromagnetic resonance frequency. Compared with the pure
ferromagnetic film, a larger Faraday rotation angle is obtained in our
model, which may be useful for the application of
magneto-optical devices. 相似文献
11.
《Waves in Random and Complex Media》2013,23(2):211-223
AbstractIn this study, we explain an approach including conversion from constitutive parameters to dispersive transmission line parameters using the double-band DNG (double-negative) properties of the circular type fishnet metamaterials. After designing the metamaterial structure, the numerical calculations and the composite right/left-handed (CRLH) modeling of circular-type metamaterials are realized in free space. Detailed dispersion characteristics give us the opportunity to explain the true behavior of the inclusions during the analysis stage. By combining the results coming from the standard retrieval procedure with the conventional CRLH theory, we calculate the actual values of the transmission line parameters for all frequency regimes. The constitutive parameters of an equivalent CRLH transmission line are derived and shown to be negative values. It is shown that the constitutive parameters present the same behavior for all negative refractive index regimes. The double-negative properties and the phase advance/lag behavior of metamaterials are observed based on the dispersive transmission line parameters. 相似文献
12.
The phenomena of super energy flows are studied theoretically and numerically in a parallel-plate waveguide which is filled with two layered equally-thick different media, i.e. air and specific left-handed materials (LHM) with εr1 = -1/(1 +δ) +iγ and μr1 = -(1 + δ) + iγ. In this special waveguide, two-directional super-energy flows are excited by a three-dimensional horizontal electric dipole at the same time, which has transmission patterns different from those of two-dimensional source and three-dimensional vertical electric dipole. We also show that the retardation and loss in LHM are sensitive to the amplitude of super power densities, and the dimensions of waveguide determine the propagating modes, which makes super energy flows more practical. 相似文献
13.
We have investigated the transmission ability of a layered structure the central layer of which is made of a “left-handed” material (its refractive index is negative) and is separated by two air slabs from a “right-handed” dielectric medium that surrounds the structure. We consider tunneling of energy fluxes through the structure and determine conditions for the complete (reflectionless) transmission of the power of the incident wave through it. We show that this effect is resonant and is observed when the tangential component of the wave vector of the incident wave coincides with the longitudinal wave vector of one of waveguiding eigenmodes of the left-handed layer. 相似文献
14.
The phenomena of super energy flows are studied theoretically and
numerically in a parallel-plate waveguide which is filled with two
layered equally-thick different media, i.e. air and specific
left-handed materials (LHM) with $\epsilon_{{\rm
r}1}=-1/(1+\delta)+\i\gamma$ and $\mu_{{\rm
r}1}=-(1+\delta)+\i\gamma$. In this special waveguide,
two-directional super-energy flows are excited by a three-dimensional
horizontal electric dipole at the same time, which has transmission
patterns different from those of two-dimensional source and
three-dimensional vertical electric dipole. We also show that the
retardation and loss in LHM are sensitive to the amplitude of super
power densities, and the dimensions of waveguide determine the
propagating modes, which makes super energy flows more practical. 相似文献
15.
Min-Hua LiHe-Lin Yang Yan TianDong-Yun Hou 《Journal of magnetism and magnetic materials》2011,323(5):607-610
A kind of planar left-handed metamaterial (LHM) with unique configurations is demonstrated, which offers an approach in building dual-band negative-index materials. Simulated and experimental results predict two left-handed transmission bands near 11.1 and 14.6 GHz. Dual bands of negative refractive indexes are verified using the retrieval procedure. Field and current distribution at the dual magnetic resonance are also examined. The effective electromagnetic parameters show that by carefully adjusting dimensions of the unit cell, electric and magnetic resonances can be coexistent at some frequency ranges with both negative permittivity and negative permeability. The idea can help us designing planar negative-index materials with multibands. 相似文献
16.
The characteristics of an imaging system formed by a left-handed material (LHM) slab of finite length are studied, and the influence of the finite length of the slab on the image quality is analyzed. Unusual phenomena such as surface bright spots and negative energy stream at the image side are observed and explained as the cavity effects of surface plasmons excited by the evanescent components of the incident field. For a thin LHM slab, the cavity effects are found rather sensitive to the length of the slab; the bright spots on the bottom surface of the slab may stretch to the image plane and degrade the image quality. 相似文献
17.
We study the surface polaritons and optical transmission in multi-layer structures containing alternate anisotropic left-handed
materials and isotropic right-handed materials. By means of the transfer matrix method, the dispersive relations of the surface
polaritons are derived. In contrast to the single left-handed slab, the multi-layer structure is capable of supporting more
surface polaritons due to the existence of more interfaces between the left-handed and right-handed layers. We further make
detailed investigations of the optical transmission associated with the surface polaritons. Numerical results show that the
variance of the thickness of each layer will obviously affect the positions of the transmission peaks, corresponding to the
surface polariton branches. Moreover, the presence of the absorption in the anisotropic left-handed materials plays a crucial
role in the optical transmission spectra.
PACS 41.20.Jb; 73.20.Mf; 78.20.Bh; 42.70.Qs 相似文献
18.
We present the design of a Multiband two-handed metamaterial (MM) with the composite structure combined ring and cross pairs (RP + CP) in the terahertz regime. The dual-band left-handed and single-band right-handed transmission properties of this composite structure were explored by the FDTD method. The MM exhibits left-handed and right-handed transmission pass bands around the frequencies of 0.43 THz, 1.32 THz and 0.85 THz for the terahertz electromagnetic (EM) wave normal incidence, respectively. The surface currents distributions are demonstrated to discuss the physical mechanism of the left-handed properties of the proposed MM. The retrieved equivalent EM parameters and the refraction phenomenon based on a wedge-shaped model verify the left-handed properties. Furthermore, the dual-band left-handed transmission properties of RP + CP structure can be tunable individually by changing the structural parameters. The presented design of terahertz two-handed MM offers a flexibility for investigation of their novel EM properties, and important terahertz device applications. 相似文献
19.
The nonlinear properties of lattice network-based(LNB) composite right-/left-handed transmission lines(CRLH TLs)with nonlinear capacitors are experimentally investigated.Harmonic generation,subharmonic generation,and parametric excitation are clearly observed in an unbalanced LNB CRLH TL separately.While the balanced design of the novel nonlinear TL shows that the subharmonic generation and parametric processes can be suppressed,and almost the same power level of the higher harmonics can be achieved over a wide bandwidth range,which are difficult to find in conventional CRLH TLs. 相似文献