缺陷对左手材料负折射的调控行为

采用电路板刻蚀技术制备左手材料样品，由劈尖法分别研究了无缺陷和引入缺陷时左手材料的负折射特性.实验结果表明，引入两种点缺陷材料与无缺陷材料的功率峰值之比分别为1.035和1.256，且负折射率的绝对值分别增大了9.6%和19.6%；引入空位缺陷材料与无缺陷材料的功率峰值之比最大为1.973，最小为0.364，负折射率的绝对值最大增大了68.3%，最小增大了9.6%.缺陷的存在改变了左手材料周期性结构，形成新的电磁谐振条件，使其负折射率和功率峰值发生了变化，实现了对左手材料负折射率的调控. 关键词： 左手材料 负折射 缺陷     

Imaging properties of uniaxially anisotropic negative refractive index materials

The imaging properties of uniaxially anisotropic negative refractive index materials have been investigated theoretically. Based on an accurate theoretical formulation, we have discussed in detail whether and under what conditions the slabs of uniaxially anisotropic negative refractive index materials will have the power to focus perfectly all Fourier components of an image. It was shown that if the effects of absorption and dispersion can be neglected, under some particular conditions the slabs of uniaxially anisotropic negative refractive index materials will have the power to focus perfectly all E-mode or all H-mode or both E- and H-mode Fourier components of an image. It was also shown that perfect focus cannot occur in the presence of absorption and dispersion, but if the effects of absorption and dispersion are rather small, excellent focus can still occur.     

A liquid refractive index detect method based on negative refraction phenomenon in 2D photonic crystal structure

This paper is mainly concerned with the investigation of negative refraction phenomenon dependent on the background refractive index in 2D photonic crystal, which consists of a hexagonal lattice of circular dielectric rods with Si. The paper presents the relationship between background refractive index and negative refraction. The relationship is investigated by using the finite-difference time-domain (FDTD) method on software RSoft. The results point out that the output power is added with the increase of the background refractive index. With the research, a new fluid refractive index detection method is proposed. Compared with other normal liquid refractive index analyzer reported, this detector has advantages of faster detection, less stray light interference and miniaturization.     

Experimental observations of a left-handed material that obeys Snell's law

We measure two-dimensional profiles of collimated microwave beams transmitted through composite wire and split-ring resonator prisms. Prior experiments suggest these structures have a negative index of refraction, though these claims have been questioned. Our 2D measurements demonstrate that transmission obeys Snell's law with a negative index, confirming the refractive nature of this signal and refuting alternatives posed in the criticisms. In addition, we present preliminary evidence that a flat rectangular slab of this material can focus power from a point source.     

Frequency bands of negative refraction in finite one-dimensional photonic crystals

We have discussed theoretically the negative refraction in finite one-dimensional (1D) photonic crystals (PCs) composed of alternative layers with high index contrast. The frequency bands of negative refraction are obtained with the help of the photonic band structure, the group velocity and the power transmittance, which are all obtained in analytical expression. There shows negative transverse position shift at the endface when negative refraction occurs, which is analysed in detail.     

Symmetric multilayer slab waveguide structure with a negative index material: TM case

The present paper deals with the theoretical modeling of symmetrical multilayer planar waveguide structure. One of the layers is considered as a negative refractive index material. We take the appropriate field distributions for p-polarization and impose the boundary conditions to derive the mode equation and other necessary formulae for the proposed structure. The effect of the negative-index layer on the modal refractive index, power flow, and penetration depth of the waveguide is studied. Also, we compare our computed results with those obtained for a similar conventional four-layer structure. It is observed that the presence of the negative-index material reduces the power flowing in the guiding layer and enhances the power flowing in the surroundings.     

Poynting vector analysis of a superlens

A power analysis of the lossy negative refractive index or left-handed slab lens is described. The presence of vortices in the image plane is revealed with small loss or gain, and these are attributed to the influence of field growth in the evanescent spectrum.     

激光热诱导PbS纳米微粒的自陷、衍射和自散焦现象

用波长为488nm的氩离子激光与聚乙烯吡咯烷酮(PVP)修饰的PbS纳米微粒水溶胶作用,观察到了样品的自陷、衍射和自散焦现象,样品的折射率为负。测量了自陷阈值功率,计算了样品的非线性折射率n2。样品响应时间为11.86ms,且对488nm波长的光有吸收,说明样品的上述现象主要是由激光热诱导折射率的改变所引起的。     

Negative refraction and imaging beyond the diffraction limit by a two-dimensional left-handed metamaterial

We report our experimental results on two-dimensional left-handed metamaterials (LHM) exhibiting negative refraction and subwavelength imaging. Transmission and reflection spectra of LHM are studied and a left-handed transmission band is observed at the frequencies where both dielectric permittivity and magnetic permeability are negative. Impedance matching is verified both with the experiments and simulations. The two-dimensional LHM structure is verified to have a negative refractive index. We employed three different methods to observe negative refraction; refraction through prism-shaped LHM, beam shifting method, and phase shift experiments. We further demonstrated subwavelength imaging and resolution using LHM superlenses. The effect of thickness on the resolving power is investigated experimentally.     

Guided modes in the chiral negative refractive index fiber

The novel characteristics of guided modes in the chiral negative refractive index fiber are investigated theoretically in this letter.We derive the characteristic equation of guided modes.Based on two types of chiral metamaterial parameters,we present the dispersion curves,energy flux,and power of guided modes.Some abnormal features,such as the existence of surface mode and dispersion curves with different shapes,intersection of dispersion curves of different guided modes,negative energy flux in the achiral cladding,and zero power at some normalized frequencies,are found in the chiral negative refractive index fiber.     

Multiscale methods for engineering double negative metamaterials

The approach taken here solves the Maxwell equations inside metamaterial crystals directly and explicitly with no approximations made. The Bloch wave solution and dispersion relation is given by a power series in the ratio between wave number and period. Each term is iteratively defined by the solution of an auxiliary problem depending on the configuration and shapes of the scatterers. The leading order term in the power series for the dispersion relation is given by the complex effective index of refraction. The effective properties and their resonance frequencies depend explicitly on the shape of the scatterers. Double negative behavior is explicitly controlled by the location of resonance frequencies related to spectra intrinsic to the geometric configuration of the multi-phase inclusions. This provides for the rational shape design of inclusions for control of double negative behavior across prescribed frequency ranges.     

Picosecond steps and dark pulses through nonlinear single mode fibers

We experimentally observed transmission of “negative pulses” through a single mode optical fiber in conditions where self-phase modulation, due to self induced variations of silica refractive index, may be balanced by the positive group velocity dispersion (dV_g/dδ#62;0). Soliton propagation could be expected at power levels where exact compensation of these two distorsions arises. The duration of the output dark pulses, determined by SHG correlation techniques, decreases when the launched power is increased, as predicted by computer simulation. For an input peak power of 0.2 W, corresponding to the theoretical soliton peak power, the emerging dark pulse looks like the input one.     

The nonlinear refraction sign turned to reverse by intercalating cresyl violent dye into layered titanate nanosheets

Solid-state dye-doped materials are an attractive alternative to conventional liquid dye solution. In this study, the spectral characteristics of dye cresyl violet before and after intercalating into layered titanate nanosheets and forming a nanohybrid thin film were investigated by measuring absorption and fluorescence spectra. In addition, their nonlinear optical properties were studied using single beam z-scan technique under irradiation of low power continuous wave (CW) produced by DPSS laser with a wavelength of 532 nm. The nonlinear studying results reveal that the dye cresyl violet in solution has a negative nonlinear refractive index, but it reverses to positive after the dye is intercalated into layered titanate nanosheets with a negative nonlinear refractive index forming CV/HTO nanohybrid thin film. This method can provide a way to turn to reverse nonlinear refraction sign of the materials.     

Certain Properties of a Quantum Information Network Driven by External Fields

A quantum information network with the structure of the property and information characteristic is studied. Under Gaussian channel is proposed. The network topological the catastrophic and exponential external field driving, the degree distribution has the spatial and temporal characteristics, and the positive or negative power index appears, which can influence the assortativity coefficient. This is possibly helpful to open a way to using the different type of driving to introduce the expected properties for the network.     

第26届全国中学生物理竞赛(决赛)实验试题的解答与考试评析(续)

3实验试题Ⅱ的解答与评析 本实验要求研究光学玻璃材料的物理特性(波长范围为400～700 nm).3.1实验装置及材料 1)玻璃样品1个(利用ZF1光学玻璃制成的三棱镜,其顶角为60°00′,误差为2.0′).     

Role of pulse shaping in control of focus and intensity of terahertz radiation

In this work, we uncover the role of lasers pulse shaping for controlling the terahertz peaks with their separation in addition to their intensities. We have developed a mathematical model for obtaining the amplitude, frequency, and power of the emitted Terahertz radiation for the lasers whose shape is tailored based on the index and skew parameter. Then the results are compared with the case of Gaussian laser pulse in collisional plasma. We optimize the process by applying magnetic field and by varying the index of the lasers for compensating the negative influence of collisions on the THz emission. Specifically the effect of laser beam width, magnetic field and collision frequency is investigated on the electric field of the terahertz radiation and the efficiency of the mechanism.     

Stationary solutions of plane nonlinear optical antiwaveguides

Eigenvalues and eigenfunctions of stationary TE waves for plane symmetrical nonlinear waveguides are studied. For a negative refractive index difference between the core and cladding (antiwaveguide) regions are found where a continuum of eigenfunctions exist in certain energy intervals. Such regions are interpreted as regions of stability. There is possible concentration of optical power in the core as well as in the cladding in these regions. Boundary values of propagation constants for nonlinear waveguides and antiwaveguides are obtained.     

On the Einstein-Cartan cosmology vs. Planck data

The first comprehensive analyses of Planck data reveal that the cosmological model with dark energy and cold dark matter can satisfactorily explain the essential physical features of the expanding Universe. However, the inability to simultaneously fit the large and small scale TT power spectrum, the scalar power index smaller than unity, and the observations of the violation of the isotropy found by few statistical indicators of the CMB urge theorists to search for explanations. We show that the model of the Einstein-Cartan cosmology with clustered dark matter halos and their corresponding clustered angular momenta coupled to torsion can account for small-scale-large-scale discrepancy and larger peculiar velocities (bulk flows) for galaxy clusters. The nonvanishing total angular momentum (torsion) of the Universe enters as a negative effective density term in the Einstein-Cartan equations causing partial cancellation of the mass density. The integrated Sachs-Wolfe contribution of the Einstein-Cartan model is negative, and it can therefore provide partial cancellation of the large-scale power of the TT CMB spectrum. The observed violation of the isotropy appears as a natural ingredient of the Einstein-Cartan model caused by the spin densities of light Majorana neutrinos in the early stage of the evolution of the Universe and bound to the lepton CP violation and matter-antimatter asymmetry.     

色散负折射特异介质的1维光子晶体缺陷态

在1维光子晶体中引入色散负折射特异介质,分析了其介电常数和磁导率在微波区（1～10 GHz）与频率的关系。分别对以色散负折射介质为缺陷的正折射率介质光子晶体及以正折射率介质为缺陷的正负折射率介质光子晶体进行了数值仿真,得出了均匀平面电磁波在正入射和斜入射时的透射谱。结果表明:在介电常数和磁导率均为负值的不同禁带中,分别出现了单、双缺陷模。利用透射谱的这一特点,可实现单、双通道滤波。     

Nonlinear effects in photonic crystal fibers filled with nematic liquid crystals

We have investigated the nonlinear propagation of light in photonic crystal fibers filled with nematic liquid crystals. We analyzed a configuration with a periodic modulation of the refractive index corresponding to a matrix of waveguides. Matrices of coupled waveguides allow observing a variety of new phenomena both for low power light beam propagation and with an existence of nonlinear effects. The opportunity for the creation of solitary waves caused by the interplay between diffraction and nonlinear effects in these kinds of fibers is investigated. At low power the propagating light beam spreads as it couples to more and more waveguides. When the intensity is increased the light modifies the refractive index distribution, inducing a defect in the periodic structure. The creation of such a defect can lead to a situation in which the light becomes self-localized and its diffractive broadening is eliminated. Eventually, in the case of positive Kerr-type nonlinearity, a discrete soliton can be created. In the case of negative nonlinearity the refractive index decreases with the optical power and can lead to bandgap shifting. The incident beam, with a frequency initially within the bandgap, is then turned outside the bandgap resulting in the changing of the propagation effect for the discrete diffraction effect. As a consequence the delocalization of the light can be observed. Presented at 9-th International Workshop on Nonlinear Optics Application, NOA 2007, May 17–20, 2007, Świnoujscie, Poland