Branching behavior of field dynamics of resonators of left-handed materials

In this paper, we study the spatiotemporal dynamics of left-handed materials that contain nonlinear cavities. These materials, having a negative refractive index, exhibit a nonlinear electromagnetic behavior. The insertion of the left-handed material into an optical cavity results into a variety of branching behavior of optical oscillators that are degenerate. The optical Kerr cavity considered in this work contains a cubic nonlinearity. The objective of this work was to investigate how branching behavior can yield useful information about the relative amount of left-handed and right-handed material controlling the diffraction in cavity. We will apply the reductive perturbation method-based multi-equation bifurcation theory to a scalar nonlinear Schrodinger equation and show how period-doubling occurs during optical wave propagation.     

Lossy double negative guiding layer optical sensors

We proposed a three-layer waveguide as an optical sensor for homogeneous sensing applications. A guiding layer of the proposed structure is considered as lossy left-handed material (LHM) with simultaneously the complex negative electric permittivity ɛ and the complex negative magnetic permeability μ. We also assume a cladding layer to have an intensity-dependent refractive index. Sensitivity of the proposed optical waveguide sensor is derived and its dependence on different parameters of a waveguide is studied.     

Negative Refractive Index in a Four-Level Atomic System

We propose a scheme for realizing negative refractive index in a four-level atomic system. It is shown that such a system can simultaneously exhibit negative permittivity and negative permeability in an optical frequency range. Furthermore, by analysing the dispersion property of the left-handed material, we lind that the probe beam can be controlled from superluminal to subluminal or vice versa via choosing appropriate parameters.     

Parametrically shielding electromagnetic fields by nonlinear metamaterials

An analytical theory is developed for parametric interactions in metamaterial multilayer structures with simultaneous nonlinear electronic and magnetic responses and with a near-zero refractive index. We demonstrate theoretically that electromagnetic fields of certain frequencies can be parametrically shielded by a nonlinear left-handed material slab, where the permittivity and permeability are both negative. The skin depth is tunable, and even in the absence of material absorption, can be much less than the wavelength of the electromagnetic field being shielded. This exotic behavior is a consequence of the intricate nonlinear response in the left-handed materials and vanishing optical refractive index at the pump frequency.     

基于三角谐振环的新型六边形谐振环金属线复合周期结构左手材料性质研究

通过实验及仿真研究了三角谐振环组合新型六边形谐振环金属线复合周期结构左手材料.仿真研究了以金属铜三角开口谐振环（SRRs）为基本单元的周期结构负磁导率材料,与闭口环（CSRRs）结果对比发现三角开口谐振环能产生很好的谐振效果即能产生负磁导率,并且多层单元仿真发现多个谐振环耦合能提高谐振频率并加宽谐振频段;设计、制作并实验和仿真研究了三角开口环为基本单元的六边形谐振环金属线复合周期结构左手材料,仿真结果在98GHz附近出现良好负折射效应,实验验证在93—108 GHz出现良好负折射效应,与仿真结果具有良好的一致性.该研究对新型周期结构左手材料的研究、设计和研制具有重要的科学意义和应用前景. 关键词： 左手材料 三角环组成的六边形谐振环 负折射     

Quasi-Rayleigh light scattering by internal elements of a metamaterial in a light-carrying core of a single-mode optical fiber based on the Veselago effect

At present, single-mode optical fibers composed of metamaterials—so-called “left-handed” optical media—for the far- and mid-IR ranges have already been created. In the near future, left-handed singlemode optical fibers for the visible and near-IR ranges will be created, light-carrying cores of which will be composed by an ordered structure of dielectric elements, the dimensions of which will be much smaller than the light wavelength, while the effective refractive index of the structure will be negative; i.e., the structure will possess the so-called “Veselago effect.” We show that, because the dimensions of these dielectric elements many times exceed the dimensions of molecules of optical media, the elements should strongly scatter light, with this scattering considerably exceeding the Rayleigh (molecular) light scattering that occurs in conventional quartz single-mode optical fibers. We propose to term this phenomenon the quasi-Rayleigh light scattering. Numerical estimates of the quasi-Rayleigh light scattering for left-handed single-mode optical fibers at a light wavelength of λ = 1.55 μm have been made.     

双曲色散型单轴左手介质中的折射

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。     

基于矩形谐振环的新型复合周期结构左手材料研究

通过实验及仿真研究了基于矩形谐振环的新型三角形和三矩形开口谐振环金属线复合周期结构左手材料.仿真研究了以金属铜三角谐振环和三矩形谐振环（SRRs）为基本单元的周期结构负磁导率材料,结果显示两种谐振环均能产生很好的谐振效果,即能产生负磁导率;设计、制作并实验和仿真研究了三角谐振环和三矩形谐振环金属线复合周期结构左手材料,实验结果分别在9.5—13.3GHz和9.8—12.5GHz出现良好的负折射效应,与仿真结果具有较好的一致性.该研究对新型周期结构左手材料的研究、设计和研制具有重要的科学意义和应用前景. 关键词： 左手材料 负折射 三角形谐振环 三矩形谐振环     

左手材料与非线性光学材料界面处的内光学双稳态

从理论及数值上研究了左手材料与传统非线性材料界面处的电磁波性质。发现在界面处出现一种新的现象——光学双稳态。入射光强、入射角以及左手材料与非线性材料的磁导率比值强烈的影响光学双稳态的行为。比较了不同的电磁模式对双稳态行为的影响。结果表明在相同的参数下，TE模式比TM模式更容易获得光学双稳态。     

Simultaneous negative permittivity and permeability in a coherent atomic vapour

A new quantum optical mechanism to realize simultaneously negative electric permittivity and magnetic permeability is suggested. In order to obtain a negative permeability, we choose a proper atomic configuration that can dramatically enhance the contribution of the magnetic-dipole allowed transition via the atomic phase coherence. It is shown that the atomic system chosen with proper optical parameters can give rise to striking electromagnetic responses (leading to a negative refractive index) and that the atomic vapour becomes a left-handed medium in an optical frequency band. Differing from the previous schemes of artificial composite metamaterials (based on classical electromagnetic theory) to achieve the left-handed materials, which consist of anisotropic millimetre-scale composite structure units, the left-handed atomic vapour presented here is isotropic and homogeneous at the atomic-scale level. Such an advantage may be valuable in realizing the superlens (and hence perfect image) with left-handed atomic vapour.     

十字环型左手材料单元结构设计与仿真

提出了一种新型十字环型左手材料结构单元.该结构只需在介质板单侧蚀刻, 即可在二维方向上产生等效负介电常数和等效负磁导率.通过理论分析, 提出场-路结合的等效源分析法以计算等效介电常数、磁导率, 并据此对十字环型结构单元的左手特性激发机理进行了论证. 后采用Nicolson-Ross-Weir 等效参数法提取了十字环型单元阵列的相对介电常数和相对磁导率, 并通过棱镜实验对材料的负折射特性进行了验证.实验表明, 该左手材料在6.8-6.9 GHz频段具有二维入射左手特性. 此种左手材料制作工艺相对简单, 为左手材料在微波器件领域的应用提供了一种较为实用的设计方案.     

Tunable complex photonic chiral lattices by reconfigurable optical phase engineering

We present a novel single-step fabrication approach, based on optical phase engineering, for tunable complex photonic chiral lattices of diverse geometries in a large area. By means of engineered reconfigurable phase patterns, we computationally simulate as well as experimentally investigate these complex structures. We show the generation of both periodic right- and left-handed chiral structures as well as photonic transversely quasi-crystallographic chiral structures. These complex chiral lattices are also demonstrated in a photorefractive material, and the lattice formation is analyzed by plane-wave-guided imaging as well as diffraction pattern imaging. Furthermore, complex photonic chiral structures with engineered tunable relative phase shifts between adjacent spiral units realizable in a single step are explored and analyzed.     

左手材料光纤的标量解近似

从Maxwell方程组出发,讨论纤芯为左手材料,包层为右手材料的阶跃型光纤.在弱导的情况下,假定横向场的极化方向保持不变,推导了横向电场满足的Helmholtz方程,利用边界条件,经过数学计算,建立了左手材料光纤标量解的特征方程,画出了左手材料光纤LP01模和LP11模的色散曲线.比较左、右手材料光纤的特征方程及其相关曲线,得到了左手材料光纤的某些奇异特性.     

Photonic-resonant left-handed medium

A new scheme to realize simultaneously negative permittivity and permeability in a coherent atomic vapor medium (photonic-resonant material) via a coherent driving mechanism is suggested. It is verified that the atomic system coherently driven by a strong optical field will give rise to a negative refractive index in certain probe frequency ranges. One of the most remarkable features of the present scheme is such that a slab fabricated by the left-handed vapor medium is an ideal candidate for designing perfect lenses since the photonic-resonant atomic vapor cannot only exhibit an isotropic negative refractive index, but also provide a good impedance match at the air-medium interfaces.     

关于左手性介质几何光学的研究（二）

利用几何光学方法研究了由左手性介质制成的简单透镜的光学特性.推理分析了左手性介质透镜处球形界面的负折射规律，并依此表明了常用光学公式仍适用于左手性介质.指出了左手性介质透镜相对于用传统介质制作的普通透镜所具备的固有优点，最后证实了利用单块左手性介质透镜即可完全消球差，并相应提供了零球差左手性介质透镜的设计实例.     

Optical bistability with surface polaritons in layered structures containing left-handed metallic magnetic composites

We present the exact results on optical bistability (including angular and frequency bistabilities) with surface polaritons in layered structures containing left-handed metallic magnetic composite (MMC). The bistable behaviors of the reflected field are revealed for the Kretschmann and Sarid geometries, respectively. The results show that the properties of the angular and frequency bistabilities are quite similar, namely, the optical bistability with the surface polaritons can occur only when the angle or frequency detunings and the substrate’s nonlinear coefficient have the same sign. For the Kretschmann geometry, the surface polaritons can exist in the pass band due to the negative refraction effect. In the Sarid geometry, the excitation of the long-range surface polaritons in the stop band results in a lower optical bistability threshold compared with the Kretschmann geometry. The above conclusions are valid only for the frequency range where the MMC is left-handed.     

THz频段单面左手材料的设计及仿真研究

本文运用等效参数提取方法验证了双线螺旋结构在不同频率处不仅能够实现负的磁导率, 而且可以实现负的介电常数. 在电磁波平行和垂直入射到双线螺旋结构表面两种情况下, 发现其负介电常数的形成机理相同. 以往的单面左手材料的研究仅仅局限于微波波段, 通过改进双线螺旋结构, 在THz频段设计出一种新型单面左手材料, 同时利用LC等效电路解释了其设计原理. 一般的左手材料是由刻蚀在基板两侧的电谐振器和磁谐振器组合而成的复合结构, 与这些复合结构相比, 这种新型单面左手材料具有低损耗, 结构简单, 易于加工等优点.     

Resonant tunneling of a wave through a structure that contains a layer with a negative refractive index

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.     

Right handed or left handed? Forbidden x-ray diffraction reveals chirality

Enantiomers, or stereoisomers, have crystal structures that are mirror images of each other and are thus handed, like our right and left hands. The physical properties of enantiomers are identical except for optical activity, which rotates linearly polarized light by equal amounts but in opposite directions. While conventional x-ray Bragg diffraction can determine crystal structures, it does not distinguish between right- and left-handed crystals. We show resonant Bragg diffraction using circularly polarized x rays reveals the handedness of crystals by coupling x-ray helicity to a crystal screw axis. The intensity of resonantly allowed reflection of alpha-quartz is well described by an admixture of a parity-even and a parity-odd process. Our results are of general importance and demonstrate a new method to directly study chiral motifs in structures that include biomaterials, liquid crystals, magnets, multiferroics, etc.     

左手材料中圆偏振光束的反常旋转特性研究

根据Whittaker标量势理论,建立了圆偏振光束的矢量传输模型.基于这一模型研究了圆偏振光束在左手材料中的反常旋转特性.通过分析光束偏振态、衍射对强度质心旋转特性的影响,发现圆偏振光束在左手材料中旋转方向反转并揭示其旋转角等于古伊相.采用分析横向能流的方法,揭示左手材料中反向的横向能流是导致反常旋转特性的主要原因.对圆偏振光束在左手材料中反常旋转特性的研究,有利于增强对左手材料中光束传输特性的认识. 关键词： 左手材料 圆偏振光束 旋转特性