共查询到20条相似文献,搜索用时 484 毫秒
1.
光子扫描隧道显微镜球形样品二维近场强度分析 总被引:6,自引:2,他引:4
采用时域有限差分方法计算全内反射和光子扫描隧道显微镜系统。光子扫描隧道显微镜的基本工作原理是隐失波的产生和探测,当入射光在两种介质的分界面上发生全内反射,并在界面处产生非辐射的电磁波——隐失波时,采取对两界面入射光进行分别设置的方法即“三波法”设置入射激励元。分别计算一个球和两个球形样品的近场分布,并计算散射小球为探针,一个球为样品的扫描图像。结果表明:采用二维时域有限差分方法计算能较直观地显示样品表面的近场分布。表明时域有限差分方法在光子扫描隧道显微镜理论研究中具有很大潜力。 相似文献
2.
Günter Nimtz 《Foundations of Physics》2011,41(7):1193-1199
Experiments with evanescent modes and tunneling particles have shown that (i) their signal velocity may be faster than light,
(ii) they are described by virtual particles, (iii) they are nonlocal and act at a distance, (iv) experimental tunneling data
of phonons, photons, and electrons display a universal scattering time at the tunneling barrier front, and (v) the properties
of evanescent, i.e. tunneling modes are not compatible with the special theory of relativity. 相似文献
3.
F. Xi L. Hu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(2):33
We investigate the properties of electromagnetic wave propagating in a one-dimensional photonic crystal (PC) consisting of
two metamaterials with different dispersive model. The reflection gaps of metamaterials multilayer system are independent
of the incident angle. Not only TE wave but also TM wave, the omnidirectional reflection gaps exhibit the same behavior with
different incident angle for metamaterials as double negative material. We also observed that the frequency regimes of zero-transmission
bands are different for TE and TM wave with the same incident angle, when one of metamaterials is the permittivity negative
(ε < 0) and the other is the double negative. Correspondingly, we show that the result can be act as an efficient polarization
splitter. At last, we discuss the resonant tunneling effect. If the total reflection condition is satisfied, the resonant
tunneling effect is enhanced as the incident angle increases, even though the propagation wave is evanescent wave in the single
layer medium. 相似文献
4.
本文分析了由负介电常数材料和负磁导率材料交替排列组成的一维三层结构中的电磁波模式,包括传播模及波导模.传播模对应于入射的行波模,着重研究了发生共振隧穿时场分布和透射谱随入射角度的变化关系,发现改变结构参数时共振隧穿频率会劈裂成两个,且这两个隧穿模的频率间距随着中间层厚度的减小而逐渐加大.波导模是指在结构两边的半无限真空中以倏逝场形式存在的电磁模式,分析了它的存在条件即色散关系,发现这种模在材料的交界面处会出现较强的局域场.
关键词:
单负材料
共振隧穿
传播模
波导模 相似文献
5.
We compare microwave tunneling experiments using three types of potentials with calculations describing these systems, using only Maxwell's equations. The values obtained are identical within a very narrow error limit. Thus, microwave tunneling through evanescent waveguide regions, including superluminal tunneling velocities, is described by Maxwell's equations. The dispersion relation yields purely imaginary, complex, or real k-values. As an analogy, microwave tunneling presents an ideal tool for studying quantum mechanical tunneling. 相似文献
6.
We reveal that the overall evanescent wave (EW) power captured by an unclad multimode fiber employed in a sensing configuration is determined by the tunneling modes, not the guided modes. While enormous in strength, most of this power is inaccessible using traditional EW power enhancers. However, we found that by roughening the fiber end face, this supposedly lost power can be recaptured and thus can boost the detectable power level significantly. Intensive mode mixing events across various mode categories are proposed to interpret the observed phenomenon. 相似文献
7.
双轴晶体薄膜光学隧道效应 总被引:2,自引:1,他引:1
本文提出了一种研究晶体薄膜光学隧道效应的方法。我们计算了在最一般情况下双轴晶体中迅衰波的复折射率和复折射角。我们也讨论了隧道效应时晶体薄膜的反射和透射系数,找到了这些系数和薄膜光学参量的关系。这提供了用光学隧道效应检测晶体薄膜的理论基础。 相似文献
8.
Contrary to mechanical waves, the two‐slit interference experiment of single photons shows that the behavior of classical electromagnetic waves corresponds to the quantum mechanical one of single photons, which is also different from the quantum‐field‐theory behavior such as the creations and annihilations of photons, the vacuum fluctuations, etc. Owing to a purely quantum effect, quantum tunneling particles including tunneling photons (evanescent modes) can propagate over a spacelike interval. With this picture we conclude that the superluminality of evanescent modes is a quantum mechanical rather than a classical phenomenon. 相似文献
9.
T.B. Wang 《Physics letters. A》2008,373(1):169-172
Complete band gaps are found in one-dimensional photonic crystals composed of negative-permittivity and negative-permeability materials. The mechanism of these complete band gaps, unlike the Bragg complete gaps formed by interferences of forward/backward propagating waves, originate from the evanescent wave tunneling in the single-negative materials is reported for the first time. Moreover, it is also reported for the first time that both Bragg complete gaps and evanescent wave tunneling complete gaps exist in a three-constituent one-dimensional photonic structure simultaneously. 相似文献
10.
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12.
Y. Ben-Aryeh 《Applied physics. B, Lasers and optics》2006,84(1-2):121-124
The tunneling of evanescent waves into propagating waves is related to the convolution of the high spatial frequencies of
the source with those of the detectors. Such an approach is demonstrated by treating the evanescent waves which are diffracted
from very narrow apertures in a plane screen (with dimensions much smaller than the wavelength) and are converted to propagating
waves by tip detectors. The mechanism responsible for the conversion of evanescent waves into propagating waves is explained
and a general formula for the conversion of evanescent waves into propagating waves is derived.
PACS 42.25.Fx; 42.30.Kq; 42.25.Bs 相似文献
13.
StudiesofimagingexperimentforphotonscanningtunnelingmicroscopyGUONing;WUShifa;XIADekuan;CHUShicao(DalianUniversityofTechnolog... 相似文献
14.
P. E. Allain J. N. Fuchs 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(3):301-317
This article provides a pedagogical review on Klein tunneling in graphene, i.e. the
peculiar tunneling properties of two-dimensional massless Dirac electrons. We consider two
simple situations in detail: a massless Dirac electron incident either on a potential step
or on a potential barrier and use elementary quantum wave mechanics to obtain the
transmission probability. We emphasize the connection to related phenomena in optics, such
as the Snell-Descartes law of refraction, total internal reflection, Fabry-Pérot
resonances, negative refraction index materials (the so called meta-materials), etc. We
also stress that Klein tunneling is not a genuine quantum tunneling effect as it does not
necessarily involve passing through a classically forbidden region via evanescent waves. A
crucial role in Klein tunneling is played by the conservation of (sublattice) pseudo-spin,
which is discussed in detail. A major consequence is the absence of backscattering at
normal incidence, of which we give a new shorten proof. The current experimental status is
also thoroughly reviewed. The Appendix contains the discussion of a one-dimensional toy
model that clearly illustrates the difference in Klein tunneling between mono- and
bi-layer graphene. 相似文献
15.
Liwei Zhang Guiqiang Du Yewen Zhang 《Applied Physics A: Materials Science & Processing》2012,109(4):851-856
We present a theoretical investigation into the energy transport and transient wave propagation in metamaterial tunneling structures consisting of ??-negative (ENG) and ??-negative (MNG) materials. It is proved that a conjugated matched ENG/MNG bilayer and a (zero-index-material doped) photonic crystal heterostructure can work as a sub-wavelength resonator at tunneling frequency. The tunneling modes need a certain time to achieve the steady state and the charge up characteristic time increases (nearly) exponentially with the thickness of the structures. Under the steady state, the wave in the single-negative-material structures is not evanescent, but a hybrid of a traveling wave and a reactive standing wave. The phase difference between the electric field and the magnetic field varies with the position and time. The investigation of transient wave propagation in the metamaterial tunneling structures will help us to understand the interaction process between wave and metamaterial and to design special functional apparatus. 相似文献
16.
Within the band gap of a semiconductor no electronic propagating states are allowed, but there exist evanescent states which govern charge transport such as tunneling. In this Letter, we address the issue of their spin dependence in III-V semiconductors. Taking into account the spin-orbit interaction, we treat the problem using a k . p 14 x 14 Hamiltonian that we numerically compute for GaAs. Our results show that the removed spin degeneracy in the band gap can lead to giant energy splittings and induces forbidden zones in space where evanescent states are suppressed. 相似文献
17.
Y. Ben-Aryeh 《Applied physics. B, Lasers and optics》2008,91(1):157-165
The convolution between spatial modes of two different parts of an optical system can convert evanescent waves into propagating
waves. This principle is applied to different optical systems for analyzing various effects in transmission enhancements experiments.
We discuss here the differences between the present principle which is related to broadening of resonances and the near-field
optical microscopy based on a tunneling effect by a tip detector. The present analysis is applied in particular to two systems:
a) transmission enhancement in one slit by coupling the transmitted radiation with transversal Fabry–Pérot electromagnetic
(EM) modes, and b) transmission enhancement by coupling between a metallic film with arrays of holes and surface plasmons
(SP). The present approach gives more information on transmission enhancement phenomena than that obtained by conventional
treatments and can also solve certain disagreements between different theories. The differences between the present process
of converting evanescent waves into propagating waves, and that related to the new development of getting a super-resolution
by an hyperlens are discussed.
PACS 41.20.Jb; 73.20.Mf; 42.79.Dj 相似文献
18.
Hassan Bassereh Vahid Salari Farhad Shahbazi Tapio Ala-Nissila 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(6):111
We consider quantum excitation energy transport (EET) in a network of two-state nodes in the Markovian approximation by employing the Lindblad formulation. We find that EET from an initial site, where the excitation is inserted to the sink, is generally inefficient due to the inhibition of transport by localization of the excitation wave packet in a symmetric, fully-connected network. We demonstrate that the EET efficiency can be significantly increased up to ≈100% by perturbing hopping transport between the initial node and the one connected directly to the sink, while the rate of energy transport is highest at a finite value of the hopping parameter. We also show that prohibiting hopping between the other nodes which are not directly linked to the sink does not improve the efficiency. We show that external dephasing noise in the network plays a constructive role for EET in the presence of localization in the network, while in the absence of localization it reduces the efficiency of EET. We also consider the influence of off-diagonal disorder in the hopping parameters of the network. 相似文献
19.
Westenhoff S Beenken WJ Friend RH Greenham NC Yartsev A Sundström V 《Physical review letters》2006,97(16):166804
In isolated conjugated polymers two explanations are in discussion for the redshift of the emission on a picosecond time scale-exciton energy transfer (EET) between conjugated segments along the chains and conformational changes of these segments themselves, i.e., torsional relaxation. In order to resolve this question we perform femtosecond time-resolved transient absorption measurements of the energy relaxation of poly[3-(2,5-dioctylphenyl)thiophene] in toluene solution. We show that torsional relaxation can be distinguished from EET by site-selectively exciting low-energy conjugated segments. We present a unified model that integrates EET and torsional dynamics. In particular, comparison to ultrafast depolarization measurements shows that torsional dynamics cannot be neglected when analyzing EET dynamics and furthermore reveals that the exciton extends itself by about 2 monomer units during torsional relaxation. 相似文献
20.
Degenerate band edges (DBEs) of a photonic bandgap have the form (ω-ω(D)) ∝k(2m) for integers m>1, with ω(D) the frequency at the band edge. We show theoretically that DBEs lead to efficient coupling into slow-light modes without a transition region, and that the field strength in the slow mode can far exceed that in the incoming medium. A method is proposed to create a DBE of arbitrary order m by coupling m optical modes with multiple superimposed gratings. The enhanced coupling near a DBE occurs because of the presence of one or more evanescent modes, which are absent at conventional quadratic band edges. We furthermore show that the coupling can be increased or suppressed by varying the number of excited evanescent waves. 相似文献