共查询到20条相似文献,搜索用时 452 毫秒
1.
Shuai Feng Yuxi Li Bo Lei Jieying Hu Yiquan Wang Wenzhong Wang 《Solid State Communications》2012,152(11):929-932
Imaging properties and negative refraction of the two-dimensional metallic photonic crystal (PC) consisting of a triangular lattice of silver rods immersed in a dielectric is studied. It is found that good-quality image spots and negative refraction with an effective refractive index of ?1 can be achieved for the near-infrared frequency through the adjustment of the metallic PC's lattice constant and the permittivity of the background material together. Drude dispersion model is adopted to describe the silver rod and it is found that the influence of the metal's absorption is trivial to debase the quality of the image spot. 相似文献
2.
Negative refraction, which reverses many fundamental aspects of classical optics, can be obtained in systems with negative magnetic permeability and negative dielectric permittivity. This Letter documents an experimental realization of negative refraction at millimeter waves, finite magnetic fields, and cryogenic temperatures utilizing a multilayer stack of ferromagnetic and superconducting thin films. In the present case the superconducting YBa2Cu3O7 layers provide negative permittivity while negative permeability is achieved via ferromagnetic (La:Sr)MnO3 layers for frequencies and magnetic fields close to the ferromagnetic resonance. In these superlattices the refractive index can be switched between positive and negative regions using external magnetic field as tuning parameter. 相似文献
3.
Jin-Xing TaYu-Ling Song Xuan-Zhang Wang 《Journal of magnetism and magnetic materials》2012,324(1):72-77
Transmission, refraction and absorption properties of an antiferromagnetic/ion-crystal superlattice are investigated. The transmission spectra based on FeF2/TlBr superlattices reveal that there exist two intriguing guided modes in a wide stop band. Additionally, FeF2/TlBr superlattices possess either the negative refraction or the quasi left-handedness, or even simultaneously hold them at certain frequencies of two guided modes, which require both negative magnetic permeability of antiferromagnetic layers and negative permittivity of ion-crystal layers. Frequency regimes of the guided modes will be dependent on the magnitude of the external magnetic field. Therefore, handedness and refraction properties of the system can be manipulated by modifying the external magnetic field. Absorption spectra exhibit that absorption corresponding to guided modes is noticeable. 相似文献
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This paper studies a small f-number metallic lens with depth-modulated slits.Slits filled with dielectric between silver plates are designed to produce desired optical phase retardations based on the particular propagation properties of surface plasmon polaritons in nanostructures.Numerical simulation of this structure is performed through the finitedifference time-domain method.Different from the conventional dielectric lens,the metallic lens can be used as a pure phase element without energy loss brought by the light refraction at curved surfaces and total internal reflection.The focusing performance is consequently improved,with larger diffraction efficiency than that of the same shaped dielectric lens. 相似文献
6.
Refraction of light at an interface between a homogeneous dielectric and a two-dimensional photonic crystal is studied. Using the isofrequency method, various cases of refraction, including a change in the magnitude and direction of the wave vector of the incident wave, in the refractive indices of the media, and in the mutual orientation of the interface and the translation vectors of the photonic crystal, are investigated. Different types of refraction and the possibilities for realizing negative and multiwave refraction are considered. 相似文献
7.
《Superlattices and Microstructures》1987,3(3):251-256
Recent research of superlattices and multiple quantum wells has generated considerable interest in the optical waveguiding properties of these structures for optoelectronic applications. As a result we present a theoretical study of the index of refraction of superlattices and determine its variation as a function of frequency and the superlattice parameters, i.e., layer width and AlAs composition. Γ-region exciton and valence-band mixing effects are included in the model. It is found that these two effects have an important influence on the value of the index of refraction and that superstructure effects rapidly decrease for energies greater than the superlattice potential barriers. Because of the quasi-two-dimensional character of the Γ-region excitons, our results indicate that the superlattice index of refraction can vary by ∼ 2% at the quantized, bound-exciton, transition energies. Overall, the theoretical results are in good agreement with the experimental data. 相似文献
8.
In materials with negative refraction, the direction of wave propagation is opposite to the direction of the wave vector. Using an approach that characterizes the optical response of a medium totally by a generalized dielectric permittivity, , we discuss the possibility of seeing negative refraction for optical waves in a number of nonmagnetic media. These include bulk waves in organic materials and in gyrotropic materials where additional exciton–polariton waves can have a negative group velocity. It is known that dispersion of surface waves can be engineered by tailoring a surface transition layer. We show how this effect can be used to obtain surface waves with negative refraction. 相似文献
9.
Vassilios Yannopapas 《固体物理学:研究快报》2007,1(5):208-210
Nanoparticle superlattices consisting of CuCl spheres coated with a gold (Au) nanoshell are shown to exhibit negative index of refraction in the near‐UV regime. These predictions are based on calculations of the effective refractive index by use of the extended Maxwell–Garnett theory. The results for the refractive index are supplemented by multiple‐scattering calculations of light‐transmittance curves from finite slabs of nanoparticle superlattices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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《Superlattices and Microstructures》1998,23(1):35-39
Excitonic molecules in GaAs/AlAs type-II superlattices are numerically investigated. In spite of large difference of electronic structures between type-II and type-I superlattices, variational calculations show that the configuration of particles is similar to that in type-I superlattices. This is because the layer width is smaller than the extent of excitonic wavefunctions in the direction parallel to the layers in the present superlattices. 相似文献
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The static dielectric properties of (001)(GaAs)(p)/(AlAs)(p) superlattices have been calculated as a function of their period p for 1< or = p < or =12, starting from density-functional theory. The interplay between quantum confinement and local field effects is shown to be crucial. For light polarized in the growth direction it leads to the otherwise surprising justification of the use of a classical effective medium theory, even for the smallest periods. Only the inclusion of both contributions allows in ab initio and in semiempirical calculations to reproduce the experimentally observed birefringence. 相似文献
13.
Xin Li 《Physics letters. A》2010,374(43):4479-4482
When a small particle is illuminated by a circularly polarized laser beam, the induced electric dipole moment rotates in a plane. The flow lines of the emitted electromagnetic energy are the field lines of the Poynting vector. When the particle is embedded in a dielectric, these field lines have a vortex structure, and the rotation in the vortex has the same orientation as the rotation direction of the dipole. We show that when the embedding medium is a negative index of refraction material, the direction of rotation in the vortex is reversed. 相似文献
14.
Longhi S 《Optics letters》2006,31(12):1857-1859
The possibility of controlling discrete diffraction and refraction in a multiband waveguide array by periodic waveguide bending is theoretically demonstrated. Resonance effects, leading to the enhancement or inhibition of discrete diffraction, are found and related to the quantum analog of field-induced n-photon resonances in semiconductor superlattices. A very distinct behavior for light refraction is found for odd or even resonances. In particular, for even resonances, the two-band behavior of the straight binary array is quenched, resulting in the inhibition of double refraction. 相似文献
15.
Y. Zhou 《Solid State Communications》2010,150(29-30):1382-1385
I studied theoretically the enhancement of remanent polarization and dielectric permittivity of interfacial-coupled ferroelectric superlattices based on the Landau–Ginzburg theory. Our model adopts the Landau–Khalatnikov equation to describe hysteresis behavior and takes the time-dependent space-charge-limited conductivity into account to investigate the ferroelectric and dielectric properties of ferroelectric superlattices. The results are in good agreement with recent experimental observations on the enhancement of remanent polarization and permittivity of BaTiO3/SrTiO3 superlattices and heterolayered Pb(Zr,Ti)O3 thin films. 相似文献
16.
Si/Ge应变层超晶格的椭偏光谱 总被引:2,自引:0,他引:2
测量了几种不同组分的(Si)M/(Ge)N应变超晶格材料的椭偏光谱(2.0~5.0eV),并得到了其介电函数谱;应用介电函数的临界点理论,研究了(Si)M/(Ge)N应变超晶格材料的光学性质。发现短周期Si/Ge应变超晶格除了具有明显的E1和E2带间跃迁外,还存在与应力和超晶格能带的折迭效应有关的跃迁峰,其能量分别位于2.3~3.0eV和3.3~4.0eV范围内 相似文献
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采用三维时域有限差分法(FDTD),模拟计算了光子扫描隧道显微镜(PSTM)系统中的介质和银质金属样品在不同偏振模式光源下的近场强度分布。使用介质小样品检验探针性能,在探针不同位置计算得到了相似的近场强度分布图,说明编写的程序是可信的。给出了等高扫描时p偏振和s偏振条件下,“PSTM”字样介质样品和银质金属样品上方5nm处的近场强度分布图,结果显示:对介质样品,p偏振波能较好的反映样品的形貌,这是由入射电场的方向决定的;银质金属有表面增强作用,对不同偏振波均能在某种程度上反映样品的形貌,仍有待近一步的研究。 相似文献
19.
Sheng-Feng Cheng Guo-Jun Jin 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):291-296
We investigate coupled optical interface modes in Thue-Morse (TM) dielectric superlattices composed of two kinds of materials
with frequency-dependent dielectric functions. Four basic transfer matrices are derived in the dielectric continuum approximation.
By a standard matrix operation method, the trace map of the global transfer matrix in this configuration is obtained. Under
Born-von Kármán boundary conditions, the frequency spectra are calculated and their branching rules together with the quartet property are elucidated. It is further proved rigorously that nearly all eigenmodes in this framework have extended nature. The quartet of the eigenmodes is illuminated analytically. The common features and pronounced differences compared
with coupled optical interface modes in periodic and Fibonacci dielectric superlattices as well as with other collective elementary
excitations in TM structures are also revealed.
Received 24 September 2002 / Received in final form 11 January 2003 Published online 11 April 2003
RID="a"
ID="a"e-mail: gjin@nju.edu.cn 相似文献
20.
《Superlattices and Microstructures》2000,28(3):199-206
This paper reports temperature-dependent thermal conductivity measurements in the cross-plane direction of symmetrically strained Si/Ge superlattices, and the effect of doping, period thickness and dislocations on the thermal conductivity reduction of Si/Ge superlattices. The Si/Ge superlattices are grown by molecular beam epitaxy on silicon and silicon-on-insulator substrates with a graded buffer layer. A differential 3 ω method is used to measure the thermal conductivity of the buffer and the superlattices between 80 and 300 K. The thermal conductivity measurement is carried out in conjunction with X-ray and TEM sample characterization. The measured thermal conductivity values of the superlattices are lower than those of their equivalent composition bulk alloys. 相似文献