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金属双柱metamaterial负折射特性的液晶调控 总被引:1,自引:1,他引:0
本文研究了金属双柱metamaterial对太赫兹波负折射的液晶调控。结果表明, 当液晶的介电系数从2逐渐增大到4, 产生负折射的频率从0.648 THz逐渐变化到0.413 THz, 包含了0.650 THz和0.500 THz附近两个大气窗口; 通过改变液晶的介电常数, 可以在该频段内任一频点实现负折射、零折射或正折射。由于液晶的介电常数可以通过外加交流偏压或光场进行调控, 因此利用液晶可以实现对太赫兹波负折射频率和传播方向的调控。 相似文献
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本文研究了硅柱在MnFe2O4磁性液体背景中排列成六边形结构的二维光子晶体的可调谐负折射特性. 利用平面波展开法和时域有限差分法理论研究了硅柱-磁性液体体系二维光子晶体的带隙结构、等频曲线和负折射现象随外磁场强度的变化关系. 模拟结果表明, 硅柱-磁性液体体系二维光子晶体工作在TE模式时, 其负折射特性可由外磁场调节. 在固定背景溶液的磁性颗粒体积分数和入射光频率时, 所研究的折射光束的偏转角和光子晶体的负折射率绝对值随外磁场的增大而增大, 而在固定背景溶液的磁性颗粒体积分数和外磁场强度时, 负折射角和负折射率的绝对值随入射光归一化频率增大而减小. 固定外场强度和入射光频率时, 所研究结构的负折射特性随背景溶液的磁性颗粒体积分数增大而变弱. 相似文献
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本文对用掠入射法测定透明液体的折射率这一实验中如何选择辅助棱镜,使观察的实验现象更明显进行了分析和讨论。 相似文献
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利用金纳米棒在光照射下激发表面等离激元的性质,实验研究了其在不同介电环境下的吸收光谱.通过分析纵向等离子体共振吸收峰峰位随介质折射率的变化,获得了金纳米棒表面等离激元探针测量介质折射率的经验公式为n=(385.59)-1(λ/nm-290.56).利用金纳米棒表面等离激元探针的高介电灵敏度,测试了一些未知液体的折射率,并与阿贝折射仪测量法的结果相比较.结果与分析表明,本方法较之阿贝折射仪测量介质折射率的方法具有更高的精密度.因此,表面等离探针可用于拓展大学物理实验中的介质折射率测量实验. 相似文献
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《Optik》2013,124(20):4374-4377
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. 相似文献
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P. E. Wolf F. Bonnet L. Guyon T. Lambert S. Perraud L. Puech B. Rousset P. Thibault 《The European physical journal. E, Soft matter》2009,28(2):183-198
We have investigated the formation of helium droplets in two physical situations. In the first one, droplets are atomised
from superfluid or normal liquid by a fast helium vapour flow. In the second, droplets of normal liquid are formed inside
porous glasses during the process of helium condensation. The context, aims, and results of these experiments are reviewed,
with focus on the specificity of light scattering by helium. In particular, we discuss how, for different reasons, the closeness
to unity of the index of refraction of helium allows in both cases to minimise the problem of multiple scattering and obtain
results which it would not be possible to get using other fluids. 相似文献
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We present a design of an infrared cylindrical cloak using nanosphere dispersed nematic liquid crystal (NLC) metamaterial following the approach of Smith's group [Science 314, 977 (2006)]. Cloaking conditions require spatial distribution of liquid crystal birefringence with constant extraordinary index of refraction and radially dependent ordinary index of refraction. An approximate analytical formula for the latter is derived. Finite element (FE) simulations confirm the cloaking effect. Owing to the tunable birefringence of the liquid crystal component, such cloaking material offers the interesting possibilities of real-time control of invisibility. The possibility of experimental realization is briefly discussed. 相似文献
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A method for the determination of parameters of the surface layer (thickness and refraction index) at the liquid-vapor interface
in binary liquid mixtures was developed. The parameters of the surface layer for the C7H14-C7F14 liquid mixture in the vicinity of the critical point, which was studied by means of ellipsometry in [1], were calculated
using the proposed method. The temperature dependences of the thickness and refraction index that were determined in the homogeneous
isotropic layer approximation at the interface liquid-vapor, show structural peculiarities that were not observed earlier.
Their appearance is explained by the possible influence of hydrodynamic processes at the boundary. 相似文献
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A. A. Karetnikov N. A. Karetnikov A. P. Kovshik E. I. Ryumtsev E. V. Aksenova E. V. Kryukov V. P. Romanov 《Optics and Spectroscopy》2010,108(6):947-953
The effect of an alternating electric field on the trajectory of an extraordinary light wave in a layer of a chiral liquid
crystal with a 180° turn of the director is studied. In this structure, in the absence of the field and at a large angle of
incidence of the light wave on the liquid crystal layer, the light undergoes refraction inside the layer. It is shown that
the deformation of the director that arises under the action of the electric field changes the character of refraction of
the extraordinary wave and the layer begins to transmit the light. The threshold voltage of this effect is determined. The
dynamics of the effect is studied. At large voltages, in addition to the extraordinary wave, an ordinary light wave is observed
in the light passed through the cell. The ordinary wave intensity is modulated by the initial frequency of the control signal,
whereas the extraordinary wave intensity is modulated by the double initial frequency. 相似文献
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Impacts of Refraction Index Mismatch on Performance of Target Detection and Imaging by Using Flat LHM Lens 下载免费PDF全文
Refraction index mismatch between flat left-handed metamaterial (LHM) lens and its surrounding medium generally destroys the focusing of flat LHM lens and degrades the performance of near-field target detection by using flat LHM lens. For LHM lens of refraction index mismatch within ±30%, numerical simulations demonstrate that lenses with large refraction index may suffer less resolution degradation than lenses with small refraction index, and the enhancement of refocused microwave backscattered from target can be subsided by up to approximately 5.5dB. The refraction index mismatch will also shift the target position in the reconstructed image so that theoretical prediction of target position needs to be modified. 相似文献
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An analysis of aligned nematic liquid crystal cells containing core-shell nanospheres shows that it is possible to devise a new type of metamaterial whose index of refraction is tunable from negative, through zero, to positive values. The design parameters for the constituents can be scaled for application in the optical as well as very long wavelength (e.g., terahertz and microwave) regions. 相似文献
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Francisco Javier González 《Optics Communications》2011,284(5):1429-1434
In this work the resonance, frequency response, and far-field patterns of an optical nano-antenna placed on an interface between air and a metamaterial substrate is obtained through finite element calculations. The metamaterial is characterized by an effective, macroscopic index of refraction which can take negative and near-zero values, or by published values of the effective permittivity and permeability for metamaterials. The results show that the resonant wavelength and response can be fitted to analytical functions that are even functions of the index of refraction, this is consistent with the knowledge that negative indices of refraction allows for wave propagation in the same magnitude but opposite direction observed with positive indices of refraction. The simulations also show that substrates with near-zero index of refraction will enhance the antenna response by 62% compared to substrates with n > 1. Lossy metamaterials are also considered in the simulations. The far-field pattern of the antenna, obtained through a near-field to far-field transformation, behaves the same independently of the sign of the index of refraction, also the far-field pattern for the emission towards near-zero substrates is nearly constant and independent of the angle for the evaluated angular range. 相似文献
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悬浊液光谱透射法测量烟尘粒子的复折射率 总被引:1,自引:0,他引:1
光谱复折射率是计算烟尘粒子散射特性的重要参数。该文在光谱透射法反演烟尘粒子复折射率理论的基础上,将烟尘粒子弥散于水中形成烟尘粒子悬浊液,通过可见光分光光度计测量该悬浊液的光谱透射率,通过激光粒度仪获得烟尘粒子的粒径分布,利用悬浊液光谱透射法对烟尘粒子的复折射率进行了反演。研究结果表明,烟尘粒子在可见光波长范围内没有明显吸收带,但随着波长的增加,透过率逐渐降低。烟尘粒子复折射率的反演结果与KBr样片法的反演结果吻合较好。利用悬浊液光谱透射法测量烟尘粒子的复折射率,实验过程简单,约束条件少,并可利用红外分光光度计测量透射率后,拓展至红外波段。 相似文献
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Effect of concentration of Er3+ ions on ultra-large index of refraction via atomic coherence in Er3+: YAG crystal 下载免费PDF全文
A four-level system is proposed to produce large index of refraction accompanied by vanishing absorption in the Er^{3+}-doped yttrium aluminium garnet (YAG) crystal. It is found that the high index of refraction with zero absorption can be provided by adjusting the incoherent pumping, the coherent field, as well as the concentration of Er^{3+} ions in the crystal. Furthermore, the value of the incoherent pump to achieve the high index of refraction with zero absorption is greatly changed with increasing the concentration of Er^{3+} ions in the crystal. This indicates that the effect of concentration on the high index of refraction with zero absorption cannot be neglected. 相似文献