可见光波段负折射材料的研究
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摘要
负折射是一种违反常规的电磁波穿越光学界面的现象,表现为入射光和折射光位于界面法线的同侧。平板负折射材料制备的透镜,其成像分辨率可以突破衍射极限,还可以用于具有军事意义的隐身设备。除此之外,负折射材料在位相补偿、纳米波导等一系列光学领域,具有巨大的潜在应用价值,因此成为近十年的研究热点。
2000年,D.R.Smith等人把金属微结构的线阵列和开口谐振环阵列组合,首次在实验上观测到负折射,其现象出现在微波波段。之后有人采用金属渔网结构的材料把负折射波段推至可见光的边缘。2008年,张翔组利用直径60nm的银线阵列实验上获得了660nm光波的负折射,但是4.5μm厚材料的透过率仅4%。
本论文深入研究银线阵对电磁波反作用的等离子体微观机理,获得抑制银纳米材料在可见光波段的光能损耗的趋肤效应尺寸约20nm。据此首先提出利用液晶分散直径仅20nm银纳米球阵列在可见光波段实现负折射,其中银纳米球间距为40nm。理论分析表明,液晶的An越大,获得负折射的波段越宽；预计△n为0.22的E7液晶/银纳米球复合材料的负折射波段在460nm-485nm范围。实验发现银纳米球极易团聚,导致这种负折射材料很难制备。
理论设计直径20nmm的银线阵列在可见光波段实现负折射需要银线间距小于70nm。自制了氧化铝阵列孔模板,利用电沉积法在模板上获得了直径40nm、线间距110nm的银线阵列材料,反射率检测结果表明在可见光边缘780nm波长处材料沿线介电分量值约为-2.33,证明为负折射材料。为进一步提高透过率,提出在反六角液晶分子模板中生长直径20nm、线间距40nm的银线阵,理论计算表明在450nm-800nm宽波段可见光范围内能够产生负折射,理论预测波长大于500nm的光波的透过率大于30%。反六角溶质液晶是软模板,难以大面积制备银线阵列。
液晶分子上的共轭π电子很容易离域运动,可以在光波的电场中产生诱导偶极子,即类等离子体,液晶分子容易排列取向,同时液晶材料对可见光的吸收基本可以忽略,因此液晶负折射材料将具有高透过率。实验上证明液晶分子与光波电场约呈50°夹角时负折射角最大,且液晶中的最大负折射角与液晶的△n值近似呈线性关系。实验上获得波长532nm的TM激光在△n=0.42的液晶材料中的最大负折射角为-14°,约为已有文献报道值的2倍。
本工作深入金属等离子体和分子偶极子的电子特性,定性分析了振荡激元产生负折射的微观机理。在此基础上,借助介电常数计算模型给出一些微结构的负折射预测,探索了能够覆盖整个可见光波段的高透过率负折射材料。同时,对金属材料的能量损耗与比表面积的关系进行了分析,解明只有金属纳米线的直径小到20nm时才有可能获得有价值的负折射材料。综上,金属中的自由振荡等离子体虽然能强烈作用于电磁波、使其传播方向发生负折射偏转,但金属的光能损耗也是很难突破的瓶颈问题；而液晶中的类等离子体振荡效应,没有光能损耗问题,虽然其类等离子体的振荡目前不能在全方位产生,但有希望通过控制液晶分子的取向形式来改善,这是本研究今后要开展的工作。
Negative refraction is a kind of novel electromagnetism phenomenon. In visible optical frequencies, the propagation paths of refractive wave and incident wave are at the same side of the normal of the interface. A flat lens made of negative refraction materials (NRM) can focus light and the resolution of the image can be smaller than the diffraction limit. NRM also can be used in invisible cloak devices which qualify NRM significance in future military. Besides, NRM bring out plenty of potential applications in visible optical frequencies, such as phase compensation, nano waveguide and so on. The research of NRM in optical frequencies has become one of the most hottest fields in decade.
The artificial NRM composed of metallic wires arrays and metallic slit rings arrays was firstly detected experimentally at microwave range by D. R. Smith et al. in2000. Up to now, fishnet metamaterial has realized negative refraction at780nm. However, because of the sophistication of the cells, the NRMs are facing the challenge of the nano processing technology. Negetive refraction at660nm was obtained by silver nanowire arrays with the diameter of60nm by X. Zhang et al. in2008, but the experiment shows that the transmission is only4%/4.5μm.
The microscopic mechanism of the reaction of the silver nanoline to electromagnetic wave is studied deeply, and the skin depth is about20nm. First, silver nanospheres dispersed in liquid crystals is proposed to realize negative refraction at visible optical wavelength. Silver nanospheres with the diameter of 20nm dispersed in liquid crystals are proposed to realize negative refraction at visible optical wavelength. It demonstrates that negative refraction at visible optical wavelength can be realized when the distance between the silver nanospheres is smaller than40nm. The theory turns out that the bigger the An of the liquid crystals,the wider wavelength band of negative refraction. The negative refraction band of E7liquid crystals (An=0.22)/silver nanospheres composite material is460nm-485nm. Silver nanospheres/Liquid crystals composite materials are prepared in experiment. But the device confronts with the problem of stability due to the easy reunion of the nanospheres.
The distance of the silver nanowire arrys with diameter of20nm should be smaller than70nm for negative refraction at visible optical wavelength. The Ag/PA material with nanoline radius of20nm and the distance between adjacent lines of110nm is prepared by elecrodeposite. The reflection test shows the negative permittivity is-2.33for the wave with the wavelength of780nm, which proves Ag/PA is a kind of negative refraction materials. In order to improving the transmission, silver nanowires arrays with diameter of20nm and distance of40nm which are based on on reverse hexagonal lyotropic liquid crystal template is proposed. Theoretical calculation shows the nagative refraction waveband is450nm-800nm. Theory turns out the transmission is about30%beyond500nm, which means the multiple enhancement of transmittance.
The conjugate π electrons in liquid crystal molecule are delocalized in applied electromagnetic fields and the dipole is induced to react to the electromagnetic fields. Liquid crystals (LC) are nearly transparent for visible optical light so the NIM based on LC has the advantage of high transmittance. Experiments turns out the max negative refraction angle can be obtained when the angle between the long aix of the molecule and electric fields is about50°. Besides, the biggest negative refraction angle is akin to in linear relation with An of LC. TM wave with wavelength of532nm can realize negative refraction in LC and the negative refraction angle is about-14°or the LC with△n=0.42, which is twice of the value reported.
This work investigates the plasma of metal and dipole of the molecule and these oscillation plasmon are qualitative designed to realize negative refraction. The theoretical models of permittivity are used to predict negative refraction effect in the designed materials. All-angle negative refraction material covering almost the whole visible light is explored in this work. Meanwhile, the relation between energy loss and the specific surface area is analyzed, which turns out the radius of nanolines should be decreased to10nm to obtain valuable NRM. Though the free plasma of metal can affect electromagnetic wave strongly and change its direction of propagation, the energy loss is hard to avoid. The like-plasma of liquid crystal can't realize all-angle negative refraction, but it has the advantage of lossless. There is still hope to solve this problem by controlling the orientation form of liquid crystal molecule, which is one of our works in future.
2000年,D.R.Smith等人把金属微结构的线阵列和开口谐振环阵列组合,首次在实验上观测到负折射,其现象出现在微波波段。之后有人采用金属渔网结构的材料把负折射波段推至可见光的边缘。2008年,张翔组利用直径60nm的银线阵列实验上获得了660nm光波的负折射,但是4.5μm厚材料的透过率仅4%。
本论文深入研究银线阵对电磁波反作用的等离子体微观机理,获得抑制银纳米材料在可见光波段的光能损耗的趋肤效应尺寸约20nm。据此首先提出利用液晶分散直径仅20nm银纳米球阵列在可见光波段实现负折射,其中银纳米球间距为40nm。理论分析表明,液晶的An越大,获得负折射的波段越宽；预计△n为0.22的E7液晶/银纳米球复合材料的负折射波段在460nm-485nm范围。实验发现银纳米球极易团聚,导致这种负折射材料很难制备。
理论设计直径20nmm的银线阵列在可见光波段实现负折射需要银线间距小于70nm。自制了氧化铝阵列孔模板,利用电沉积法在模板上获得了直径40nm、线间距110nm的银线阵列材料,反射率检测结果表明在可见光边缘780nm波长处材料沿线介电分量值约为-2.33,证明为负折射材料。为进一步提高透过率,提出在反六角液晶分子模板中生长直径20nm、线间距40nm的银线阵,理论计算表明在450nm-800nm宽波段可见光范围内能够产生负折射,理论预测波长大于500nm的光波的透过率大于30%。反六角溶质液晶是软模板,难以大面积制备银线阵列。
液晶分子上的共轭π电子很容易离域运动,可以在光波的电场中产生诱导偶极子,即类等离子体,液晶分子容易排列取向,同时液晶材料对可见光的吸收基本可以忽略,因此液晶负折射材料将具有高透过率。实验上证明液晶分子与光波电场约呈50°夹角时负折射角最大,且液晶中的最大负折射角与液晶的△n值近似呈线性关系。实验上获得波长532nm的TM激光在△n=0.42的液晶材料中的最大负折射角为-14°,约为已有文献报道值的2倍。
本工作深入金属等离子体和分子偶极子的电子特性,定性分析了振荡激元产生负折射的微观机理。在此基础上,借助介电常数计算模型给出一些微结构的负折射预测,探索了能够覆盖整个可见光波段的高透过率负折射材料。同时,对金属材料的能量损耗与比表面积的关系进行了分析,解明只有金属纳米线的直径小到20nm时才有可能获得有价值的负折射材料。综上,金属中的自由振荡等离子体虽然能强烈作用于电磁波、使其传播方向发生负折射偏转,但金属的光能损耗也是很难突破的瓶颈问题；而液晶中的类等离子体振荡效应,没有光能损耗问题,虽然其类等离子体的振荡目前不能在全方位产生,但有希望通过控制液晶分子的取向形式来改善,这是本研究今后要开展的工作。
Negative refraction is a kind of novel electromagnetism phenomenon. In visible optical frequencies, the propagation paths of refractive wave and incident wave are at the same side of the normal of the interface. A flat lens made of negative refraction materials (NRM) can focus light and the resolution of the image can be smaller than the diffraction limit. NRM also can be used in invisible cloak devices which qualify NRM significance in future military. Besides, NRM bring out plenty of potential applications in visible optical frequencies, such as phase compensation, nano waveguide and so on. The research of NRM in optical frequencies has become one of the most hottest fields in decade.
The artificial NRM composed of metallic wires arrays and metallic slit rings arrays was firstly detected experimentally at microwave range by D. R. Smith et al. in2000. Up to now, fishnet metamaterial has realized negative refraction at780nm. However, because of the sophistication of the cells, the NRMs are facing the challenge of the nano processing technology. Negetive refraction at660nm was obtained by silver nanowire arrays with the diameter of60nm by X. Zhang et al. in2008, but the experiment shows that the transmission is only4%/4.5μm.
The microscopic mechanism of the reaction of the silver nanoline to electromagnetic wave is studied deeply, and the skin depth is about20nm. First, silver nanospheres dispersed in liquid crystals is proposed to realize negative refraction at visible optical wavelength. Silver nanospheres with the diameter of 20nm dispersed in liquid crystals are proposed to realize negative refraction at visible optical wavelength. It demonstrates that negative refraction at visible optical wavelength can be realized when the distance between the silver nanospheres is smaller than40nm. The theory turns out that the bigger the An of the liquid crystals,the wider wavelength band of negative refraction. The negative refraction band of E7liquid crystals (An=0.22)/silver nanospheres composite material is460nm-485nm. Silver nanospheres/Liquid crystals composite materials are prepared in experiment. But the device confronts with the problem of stability due to the easy reunion of the nanospheres.
The distance of the silver nanowire arrys with diameter of20nm should be smaller than70nm for negative refraction at visible optical wavelength. The Ag/PA material with nanoline radius of20nm and the distance between adjacent lines of110nm is prepared by elecrodeposite. The reflection test shows the negative permittivity is-2.33for the wave with the wavelength of780nm, which proves Ag/PA is a kind of negative refraction materials. In order to improving the transmission, silver nanowires arrays with diameter of20nm and distance of40nm which are based on on reverse hexagonal lyotropic liquid crystal template is proposed. Theoretical calculation shows the nagative refraction waveband is450nm-800nm. Theory turns out the transmission is about30%beyond500nm, which means the multiple enhancement of transmittance.
The conjugate π electrons in liquid crystal molecule are delocalized in applied electromagnetic fields and the dipole is induced to react to the electromagnetic fields. Liquid crystals (LC) are nearly transparent for visible optical light so the NIM based on LC has the advantage of high transmittance. Experiments turns out the max negative refraction angle can be obtained when the angle between the long aix of the molecule and electric fields is about50°. Besides, the biggest negative refraction angle is akin to in linear relation with An of LC. TM wave with wavelength of532nm can realize negative refraction in LC and the negative refraction angle is about-14°or the LC with△n=0.42, which is twice of the value reported.
This work investigates the plasma of metal and dipole of the molecule and these oscillation plasmon are qualitative designed to realize negative refraction. The theoretical models of permittivity are used to predict negative refraction effect in the designed materials. All-angle negative refraction material covering almost the whole visible light is explored in this work. Meanwhile, the relation between energy loss and the specific surface area is analyzed, which turns out the radius of nanolines should be decreased to10nm to obtain valuable NRM. Though the free plasma of metal can affect electromagnetic wave strongly and change its direction of propagation, the energy loss is hard to avoid. The like-plasma of liquid crystal can't realize all-angle negative refraction, but it has the advantage of lossless. There is still hope to solve this problem by controlling the orientation form of liquid crystal molecule, which is one of our works in future.
引文
[1]V. G. Veselago. The electrodynamics of substances with simultaneously negative values of ε and μ[J]. Physics-Uspekhi[J].1968,10(4):509-514.
[2]J. B-. Pendry. Negative-refraetion makes a perfeet lens[J]. Phys Rev Lett, 2000, 85(18):3966-3969.
[3]N. Fang, H. Lee, C. Sun, et al. Sub-Diffraction-Limited Optical Imaging with a Silver Superlens[J]. Science,2005,308:534-537.
[4]J. T.Huangfu, L. X. Ran, H. S. Chen, et al. Experimental confirmation of negative refractive index of a metamaterial composed of Omega-like metallic patterns[J]. Appl Physs Lett,2004,84(9):1537-1539.
[5]A. Alu, A. Salandrino. Negative effective permeability and left-handed materials at optical frequencies[J]. Opt Exp,2006,14(4):1557-1567.
[6]A. Ishikawa, T. Tanaka, S. Kawata. Negative magnetic permeability in the visible light region[J]. Phys Rev Lett,2005,95(23):237401.
[7]T.Taubner, D. Korobkin, Y. Urzhumov, et al. Near-field microscopy through a SiC superlens[J]. Science,2006,313(5793):1595-1595.
[8]Z.W. Liu, H. Lee, Y. Xiong, et al. Far-field optical hyperlens magnifying sub-diffraction-limited objects[J]. Science,2007,315(5819):1686-1686.
[9]Jacob, Z., L.V. Alekseyev, E. Narimanov. Optical Hyperlens Far-field imaging beyond the diffraction limit[J]. Opt Exp,2006,14(18):8247-8256.
[10]A. Salandrino, N. Engheta. Far-field subdiffraction optical microscopy using metamaterial crystals:Theory and simulations[J]. Phy Rev B,2006,74:075103.
[11]I.I Smolyaninov, Y.J. Hung, C.C. Davis. Magnifying superlens in the visible frequency range[J]. Science,2007,315:1699-1701.
[12]J.B. Pendry, D. Schurig, D. R. Smith. Controlling electromagnetic fields[J]. Science,2006,312:1780-1782.
[13]D. Schurig, J. J. Mock, B.J. Justice, et al. Metamaterial electromagnetic cloak at microwave frequencies [J]. Science, 2006, 314: 977-980.
[14]W.S.Cai, U.K. Chettiar, A.V. Kildishev, et al. Optical cloaking with metamaterials[J]. Nature Photonics,2007,1(4):224-227.
[15]R. Liu, C. Ji, J.J. Mock, et al. Broadband ground-plane cloak[J]. Science,2009, 323:366-369.
[16]J. Valentine, J. Li, T. Zentgraf, et al. An optical cloak made of dielectrics[J]. Nat Mater, 2009, 8(7):568-571.
[17]T. Ergin, N. Stenger, P. Brenner, et al. Three-dimensional invisibility cloak at optical wavelengths [J]. Science, 2010, 328:337-339.
[18]S. A. Ramakrishna. Physics of negative refractive index materials [J]. Rep Prog Phys,2005,68:449-521.
[19]C. Kittel. Introduction to Solid State Physics. Eighth Edition[M]. New Jersey: John Wiley & Sons Press,2005.
[20]P. Edward, I. Palik. Handbook of optical constants of solids [M]. San Diego: Academic Press,1985.
[21]A. M. Stefan. Plasmonics fundamental and applications [M]. New York:Springer Science+Business Media LLC,2007.
[22]H. Raether, Surface Plasmons:on Smooth and Rough Surfaces and on Gratings[M]. Berlin:Springer,1988.
[23]J. B. Pendry,, A J. Holden, W. J. Stewart, et al. Extremely low frequency plasmons in metallic mesostructures[J]. Phys Rev Lett, 1996,76(25):4773-4776.
[24]J. B. Pendry, A. J. Holden, D. J. Robbins, et al. Magnetism from conductors and enhanced nonlinear phenomena[J]. IEEE transactions on microwave theory and techniques,1999,47(11):2075-2084.
[25]G. V. Eleftheriades, K. G. Balmain. Negative-Refraction Metamaterials Fundamental principal and application[M]. John Wiley and Sons,2005.
[26]D. R. Smith, N. Kroll. Negative refractive index in left-handed materials [J]. Phys Rev Lett,2000,85(14):2933-2936.
[27]R. A.Shelby, D. R. Smith, S. Schultz. Experimental verification of a negative index of refraction[J]. Science, 2001,292:77-79.
[28]W. J. Padilla, D. N. Basov, D. R. Smith, et al. Negative refraction index metamaterials[J]. Materials,2006,9:7-8.
[29]S. Linden, C. Enkrich, M. Wegener, et al. Magnetic response of metamaterials at 100 terahertz[J]. Science,2004,306:1351-1353.
[30]C. Enkrich, M. Wegener, S. Linden, et al. Magnetic metamaterials at telecommunication and visible frequencies [J]. Phys Rev Lett, 2005,95(20): 203901.
[31]S. Zhang, W. J. Fan, B. K. Minhas, et al. Midinfrared resonant magnetic nanostructures exhibiting a negative permeability [J]. Phys Rev Lett,2005,94(3): 037402.
[32]H. K. Yuan, U. K. Chettiar, W. S. Cai, et al. A negative permeability material at red light[J]. Opt Exp,2007,15(3):1076-1083.
[33]J. Zhou, T. Koschny, M. Kafesaki, et al. Saturation of the magnetic response of split-ring resonators at optical frequencies[J]. Phys Rev Lett,2005,95(22):
[34]M. W. Klein, C. Enkrich, M. Wegener, et al. Single-slit split-ring resonators at optical frequencies:limits of size scaling[J]. Opt Lett,2006,31(9):1259-1261.
[35]V. M. Shalaev, W. Cai, U. K. Chettiar, et al. Negative index of refraction in optical metamaterials[J]. Opt Lett,2005,30(24):3356-3358.
[36]G Dolling, M. Wegener, C.M. Soukoulis, et al. Negative-index metamaterial at 780 nm wavelength[J]. Optics Letters,2007,32(1):53-55.
[37]G Dolling, C. Enkrich, M. Wegener, et al. Simultaneous negative phase and group velocity of light in a metamaterial[J]. Science,2006,312:892-894.
[38]A. Minovich, D. N. Neshev, D. A. Powell, et al. Tunable fishnet metamaterials infiltrated by liquid crystals[J]. Appl Phys Lett,2010,96(19):193103.
[39]J. Valentine, S. Zhang, T. Zentgraf, et al. Three-dimensional optical metamaterial with a negative refractive index[J]. Nature,2008,455:376-379.
[40]V. Yannopapas, A. Moroz. Negative refractive index metamaterials from inherently non-magnetic materials for deep infrared to terahertz frequency ranges[J]. J Phys:Condens Matter,2005,17:3717-3734.
[41]M. S. Wheeler, J. S. Aitchison, M. Mojahedi. Three-dimensional array of dielectric spheres with an isotropic negative permeability at infrared frequencies[J]. Phys Rev B,2005,72(19):193103.
[42]A. Garcia-Etxarri, R. Gomez-Medina, L.S. Froufe-Perez, et al. Strong magnetic response of submicron Silicon particles in the infrared[J]. Opt Exp,2011,19(6): 4815-4826.
[43]D. R. Smith,, J.B. Pendry, M.C. Wiltshire. Metamaterials and negative refractive index[J]. Science,2004,305:788-792.
[44]I. C. Khoo, D. Werner, X. Liang, et al. Nanosphere dispersed liquid crystals for tunable negative-zero-positive index of refraction in the optical and terahertz regimes[J]. Opt lett,2006,31(17):2592-2594.
[45]M. Notomi. Theory of light propagation in strongly modulated photonic crystals: Refractionlike behavior in the vicinity of the photonic band gap[J]. Phys Rev B, 2000,62(16):10696.
[46]S. Foteinopoulou, C. Soukoulis. Negative refraction and left-handed behavior in two-dimensional photonic crystals[J]. Phys Rev B,2003,67(23):235107.
[47]S. John. Strong localization of photons in certain disordered dielectric superlattices[J]. Phys Rev Lett,1987,58(23):2486-2489.
[48]E. Yablonovitch. Inhibited spontaneous emission in solid-state physics and electronics[J]. Phys Rev Lett,1987,58(20):2059-2062.
[49]J. D. Joannopoulos, Photonic crystals:molding the flow of light. Second Edition ed. New Jersey:Princeton University,2008.
[50]C. Luo, S. G. Johnson, J. Joannopoulos, et al. All-angle negative refraction without negative effective index [J]. Phys Rev B,2002,65(20):201104.
[51]P. V. Parimi, W. T. Lu, P. Vodo, et al. Negative refraction and left-handed electromagnetism in microwave photonic crystals[J]. Phys Rev Lett,2004,92(12): 127401.
[52]A. Berrier, M. Mulot, M. Swillo, et al. Negative refraction at infrared wavelengths in a two-dimensional photonic crystal[J]. Phys Rev Lett, 2004,93(7): 073902.
[53]E. Cubukcu, K. Aydin, E. Ozbay, et al. Electromagnetic waves:Negative refraction by photonic crystals[J]. Nature,2003,423:604-605.
[54]P. V. Parimi, W. T. Lu, P. Vodo, et al. Photonic crystals:imaging by flat lens using negative refraction[J]. Nature,2003,426:404.
[55]S. Zhang, W. Fan, N. C. Panoiu, et al. Experimental demonstration of near-infrared negative-index metamaterials[J]. Phys Rev Lett,2005,95(13): 137404.
[56]G. Dolling, C. Enkrich, M. Wegener, et al. Low-loss negative-index metamaterial at telecommunication wavelengths[J]. Opt Lett, 2006, 31(12): 1800-1802.
[57]S. Zhang, W. Fan, K. Malloy, et al. Demonstration of metal-dielectric negative-index metamaterials with improved performance at optical frequencies [J]. J Opt Soc Am B,2006,23(3):434-438.
[58]D. R. Smith, D. Schurig. Electromagnetic wave propagation in media with indefinite permittivity and permeability tensors[J]. Phys Rev Lett, 2003,90(7): 77405.
[59]P. A. Belov. Backward waves and negative refraction in uniaxial dielectrics with negative dielectric permittivity along the anisotropy axis[J]. Microwave and Optical Technology Letters,2003,37(4):259-263.
[60]A. J. Hoffman, L. Alekseyev, S.S. Howard, et al. Negative refraction in semiconductor metamaterials[J]. Nat Mater,2007,6(12):946-50.
[61]B. Wood, J. Pendry, D. Tsai. Directed subwavelength imaging using a layered metal-dielectric system[J]. Phys Rev B,2006,74(11):115116.
[62]A. P. Viktor, K. S. Andrey, M. S. Vladimir. Plasmon modes and negative refraction in metal nanowire composites [J]. Opt Exp,2003,11(7):735-745.
[63]W. Robyn, E. Justin, E. N. Evgenii, et al. Nonmagnetic nanocomposites for optical and infrared negative-refractive-index media[J]. J. Opt. Soc. Am. B,2006, 23(3):498-505.
[64]J. Yao, Z. Liu, Y. Liu, et al. Optical Negative Refraction in Bulk Metamaterials of Nanowires[J]. Science,2008,321:930.
[65]Y. Liu, G. Bartall, X. Zhang, et al. All-angle negative refraction and imaging in a bulk medium made of metallic nanowires in the visible region [J]. Opt Exp, 2008,16(20):15439-15448.
[66]X. Ao, S. He. Negative refraction of left-handed behavior in porous alumina with infiltrated silver at an optical wavelength[J]. Appl Phys Lett,2005,87(10): 101112.
[67]Y. Zhang,, B. Fluegel, A. Mascarenhas. Total negative refraction in real crystals for ballistic electrons and light[J]. Phys Rev Lett,2003,91(15):157404.
[68]X. Chen, M. He, Y. Du, et al. Negative refraction:an intrinsic property of uniaxial crystals[J]. Phys Rev B,2005,72(11):113111.
[69]O. P. Pishnyak, O.D. Lavrentovich. Electrically controlled negative refraction in a nematic liquid crystal[J]. Appl Phys Lett,2006,89(25):251103.
[70]Q. Zhao, L. Kang, B. Li, et al. Tunable negative refraction in nematic liquid crystals[J]. Appl Phys Lett,2006,89(22):221918.
[71]L. Kang, Q. Zhao, B. Li, et al. Experimental verification of a tunable optical negative refraction in nematic liquid crystals[J]. Appl Phys Lett,2007,90(18): 191831.
[72]Q. Zhao, J. Zhou, F. Zhang, et al. Mie resonance-based dielectric metamaterials[J]. Materials,2009,12(12):60-69.
[73]W. T. Doyle, Optical properties of a suspension of metal spheres[J]. Phys Rev B, 1989,39(14):9852-9858.
[74]H. Hovel, S. Fritz, A. Hilger, et al. Width of Cluster Plasmon Resonances-Bulk Dielectric Functions and Chemical Interface Damping[J]. Phys Rev B,1993, 48(24):18178-18188.
[75]M. M. Alvarez, J. T. Khoury, T. G. Schaaff, et al. Optical absorption spectra of nanocrystal gold molecules[J]. J Phys Chem B,1997,101(19):3706-3712.
[76]B. Palpant, B. Prevel, J. Lerme, et al. Optical properties of gold clusters in the size range 2-4 nm[J]. Phys Rev B,1998,57(3):1963-1970.
[77]M. Wheeler, J. Aitchison, M. Mojahedi. Three-dimensional array of dielectric spheres with an isotropic negative permeability at infrared frequencies[J]. Phys Rev B,2005,72:193103.
[78]M. Wheeler, J. Aitchison, M. Mojahedi. Coated nonmagnetic spheres with a negative index of refraction at infrared frequencies [J]. Phys Rev B,2006,73: 045105.
[79]M. Born, E. Wolf. Principles of Optics:Electromagnetic Theory of Propagation, Interference and Diffraction of Light[M]. Seventh Edition ed. London:Cambridge University Press,2002.
[80]马科斯.波恩,埃米尔.沃耳夫.光学原理第七版[M].北京：电子工业出版社,2007年.
[81]C. Wenshan, S. Vladimir. Optical Metamaterials[M]. New York:Springer Science+Business Media, LLC,2010.
[82]A. D. Rakic, A. B. Djurisic, J. M. Elazar, et al. Optical properties of metallic films for vertical-cavity optoelectronic devices[J]. Appl Opt,1998,37(22): 5271-5283.
[83]S. Gauza, C.H. Wen, S.T. Wu, et al. Super high birefringence isothiocyanato biphenyl-bistolane liquid crystals[J]. Japanese journal of applied physics,2004, 43(11):7634-7638.
[84]J. Li, C.H. Wen, S. Gauza, et al. Refractive indices of liquid crystals for display applications[J]. Journal of Display Technology,2005,1(1):51-61.
[85]A. Yariv, P. Yeh. Optical waves in crystals:propagation and control of laser radiation[M]. New York:John Wiley&Sons,1984.
[86]E. Spinozzil, A. Ciattoni. Ultrathin optical switch based on a liquid crystal/silver nanoparticles mixture as a tunable indefinite medium[J]. Opt Mat Exp,1(4): 732-741.
[87]D. Demus, J. Goodby, G W. Gray, et al., Physical Properties of liquid crystals. New York:Wiley,1999.
[88]I.C Khoo, Liquid Crystals. Sencond edition. New York:Wiley,2007.
[89]S. Gauza, J. Li, S. T. Wu, et al. High birefringence and high resistivity isothiocyanate-based nematic liquid crystal mixtures[J]. Liquid Crystals,2005, 32(8):1077-1085.
[90]Y. M. Liao, H. L. Chen, C. S. Hsu, et al. Synthesis and mesomorphic properties of super high birefringence isothiocyanato bistolane liquid crystals [J]. Liquid Crystals,2007,34(4):507-517.
[91]A. B. Golovin, S. V. Shiyanovskii, O. D. Lavrentovich. Fast switching dual-frequency liquid crystal optical retarder, driven by an amplitude and frequency modulated voltage[J]. Appl phys lett,2003,83(19):3864-3866.
[92]A. Kirby, G Love. Fast, large and controllable phase modulation using dual frequency liquid crystals[J]. Opt Exp,2004,12(7):1470-1475.
[93]C. A. FOSS, J. G. L. Hornyak, J. A. Stockert, et al. Template-Synthesized Nanoscopic Gold Particles:Optical Spectra and the Effects of Particle Size and Shape[J]. J. Phys. Chem, 1994,98:2963-2971.
[94]P. B. Johnson, R. W. Christy. Optical constants of noble metals[J]. Phys Rev B, 1972,6(12):4370-4379.
[95]H. Masuda, K. Fukuda. Ordered metal nanohole arrays made by a two-step replication of honeycomb structures of anodic alumina[J]. Science,1995,268: 1466-1468.
[96]M. Adachi, D. J. Lockwood. Self-Organized Nanoscale Materials[J]. New York: Springer,2006.
[97]J. Kanungo, J. Schilling. Experimental determination of the principal dielectric functions in silver nanowire metamaterials[J]. Appl Phys Lett,2010,97:021903.
[98]L. Huang, H. Wang, Z. Wang, et al. Nanowire arrays electrodeposited from liquid crystalline phases[J]. Adv Mat,2002,14(1):61-64.
[99]A. M. F Neto, S. R. A. Salinas, et al. The physics of lyotropic liquid crystals. New York:Oxford Univerity Press,2005.
[100]P. Alexandridis, U. Olsson, B. Lindman, et al. A record nine different phases (four cubic, two hexagonal, and one lamellar lyotropic liquid crystalline and two micellar solutions) in a ternary isothermal system of an amphiphilic block copolymer and selective solvents (water and oil)[J]. Langmuir,1998,14(10): 2627-2638.
[101]P. Ekwall, L. Mandell, K. Fontell, et al. Solubilization in Micelles and Mesophases and Transition from Normal to Reversed Structures[J]. Molecular Crystals and Liquid Crystals,1969,8:157-213.
[2]J. B-. Pendry. Negative-refraetion makes a perfeet lens[J]. Phys Rev Lett, 2000, 85(18):3966-3969.
[3]N. Fang, H. Lee, C. Sun, et al. Sub-Diffraction-Limited Optical Imaging with a Silver Superlens[J]. Science,2005,308:534-537.
[4]J. T.Huangfu, L. X. Ran, H. S. Chen, et al. Experimental confirmation of negative refractive index of a metamaterial composed of Omega-like metallic patterns[J]. Appl Physs Lett,2004,84(9):1537-1539.
[5]A. Alu, A. Salandrino. Negative effective permeability and left-handed materials at optical frequencies[J]. Opt Exp,2006,14(4):1557-1567.
[6]A. Ishikawa, T. Tanaka, S. Kawata. Negative magnetic permeability in the visible light region[J]. Phys Rev Lett,2005,95(23):237401.
[7]T.Taubner, D. Korobkin, Y. Urzhumov, et al. Near-field microscopy through a SiC superlens[J]. Science,2006,313(5793):1595-1595.
[8]Z.W. Liu, H. Lee, Y. Xiong, et al. Far-field optical hyperlens magnifying sub-diffraction-limited objects[J]. Science,2007,315(5819):1686-1686.
[9]Jacob, Z., L.V. Alekseyev, E. Narimanov. Optical Hyperlens Far-field imaging beyond the diffraction limit[J]. Opt Exp,2006,14(18):8247-8256.
[10]A. Salandrino, N. Engheta. Far-field subdiffraction optical microscopy using metamaterial crystals:Theory and simulations[J]. Phy Rev B,2006,74:075103.
[11]I.I Smolyaninov, Y.J. Hung, C.C. Davis. Magnifying superlens in the visible frequency range[J]. Science,2007,315:1699-1701.
[12]J.B. Pendry, D. Schurig, D. R. Smith. Controlling electromagnetic fields[J]. Science,2006,312:1780-1782.
[13]D. Schurig, J. J. Mock, B.J. Justice, et al. Metamaterial electromagnetic cloak at microwave frequencies [J]. Science, 2006, 314: 977-980.
[14]W.S.Cai, U.K. Chettiar, A.V. Kildishev, et al. Optical cloaking with metamaterials[J]. Nature Photonics,2007,1(4):224-227.
[15]R. Liu, C. Ji, J.J. Mock, et al. Broadband ground-plane cloak[J]. Science,2009, 323:366-369.
[16]J. Valentine, J. Li, T. Zentgraf, et al. An optical cloak made of dielectrics[J]. Nat Mater, 2009, 8(7):568-571.
[17]T. Ergin, N. Stenger, P. Brenner, et al. Three-dimensional invisibility cloak at optical wavelengths [J]. Science, 2010, 328:337-339.
[18]S. A. Ramakrishna. Physics of negative refractive index materials [J]. Rep Prog Phys,2005,68:449-521.
[19]C. Kittel. Introduction to Solid State Physics. Eighth Edition[M]. New Jersey: John Wiley & Sons Press,2005.
[20]P. Edward, I. Palik. Handbook of optical constants of solids [M]. San Diego: Academic Press,1985.
[21]A. M. Stefan. Plasmonics fundamental and applications [M]. New York:Springer Science+Business Media LLC,2007.
[22]H. Raether, Surface Plasmons:on Smooth and Rough Surfaces and on Gratings[M]. Berlin:Springer,1988.
[23]J. B. Pendry,, A J. Holden, W. J. Stewart, et al. Extremely low frequency plasmons in metallic mesostructures[J]. Phys Rev Lett, 1996,76(25):4773-4776.
[24]J. B. Pendry, A. J. Holden, D. J. Robbins, et al. Magnetism from conductors and enhanced nonlinear phenomena[J]. IEEE transactions on microwave theory and techniques,1999,47(11):2075-2084.
[25]G. V. Eleftheriades, K. G. Balmain. Negative-Refraction Metamaterials Fundamental principal and application[M]. John Wiley and Sons,2005.
[26]D. R. Smith, N. Kroll. Negative refractive index in left-handed materials [J]. Phys Rev Lett,2000,85(14):2933-2936.
[27]R. A.Shelby, D. R. Smith, S. Schultz. Experimental verification of a negative index of refraction[J]. Science, 2001,292:77-79.
[28]W. J. Padilla, D. N. Basov, D. R. Smith, et al. Negative refraction index metamaterials[J]. Materials,2006,9:7-8.
[29]S. Linden, C. Enkrich, M. Wegener, et al. Magnetic response of metamaterials at 100 terahertz[J]. Science,2004,306:1351-1353.
[30]C. Enkrich, M. Wegener, S. Linden, et al. Magnetic metamaterials at telecommunication and visible frequencies [J]. Phys Rev Lett, 2005,95(20): 203901.
[31]S. Zhang, W. J. Fan, B. K. Minhas, et al. Midinfrared resonant magnetic nanostructures exhibiting a negative permeability [J]. Phys Rev Lett,2005,94(3): 037402.
[32]H. K. Yuan, U. K. Chettiar, W. S. Cai, et al. A negative permeability material at red light[J]. Opt Exp,2007,15(3):1076-1083.
[33]J. Zhou, T. Koschny, M. Kafesaki, et al. Saturation of the magnetic response of split-ring resonators at optical frequencies[J]. Phys Rev Lett,2005,95(22):
[34]M. W. Klein, C. Enkrich, M. Wegener, et al. Single-slit split-ring resonators at optical frequencies:limits of size scaling[J]. Opt Lett,2006,31(9):1259-1261.
[35]V. M. Shalaev, W. Cai, U. K. Chettiar, et al. Negative index of refraction in optical metamaterials[J]. Opt Lett,2005,30(24):3356-3358.
[36]G Dolling, M. Wegener, C.M. Soukoulis, et al. Negative-index metamaterial at 780 nm wavelength[J]. Optics Letters,2007,32(1):53-55.
[37]G Dolling, C. Enkrich, M. Wegener, et al. Simultaneous negative phase and group velocity of light in a metamaterial[J]. Science,2006,312:892-894.
[38]A. Minovich, D. N. Neshev, D. A. Powell, et al. Tunable fishnet metamaterials infiltrated by liquid crystals[J]. Appl Phys Lett,2010,96(19):193103.
[39]J. Valentine, S. Zhang, T. Zentgraf, et al. Three-dimensional optical metamaterial with a negative refractive index[J]. Nature,2008,455:376-379.
[40]V. Yannopapas, A. Moroz. Negative refractive index metamaterials from inherently non-magnetic materials for deep infrared to terahertz frequency ranges[J]. J Phys:Condens Matter,2005,17:3717-3734.
[41]M. S. Wheeler, J. S. Aitchison, M. Mojahedi. Three-dimensional array of dielectric spheres with an isotropic negative permeability at infrared frequencies[J]. Phys Rev B,2005,72(19):193103.
[42]A. Garcia-Etxarri, R. Gomez-Medina, L.S. Froufe-Perez, et al. Strong magnetic response of submicron Silicon particles in the infrared[J]. Opt Exp,2011,19(6): 4815-4826.
[43]D. R. Smith,, J.B. Pendry, M.C. Wiltshire. Metamaterials and negative refractive index[J]. Science,2004,305:788-792.
[44]I. C. Khoo, D. Werner, X. Liang, et al. Nanosphere dispersed liquid crystals for tunable negative-zero-positive index of refraction in the optical and terahertz regimes[J]. Opt lett,2006,31(17):2592-2594.
[45]M. Notomi. Theory of light propagation in strongly modulated photonic crystals: Refractionlike behavior in the vicinity of the photonic band gap[J]. Phys Rev B, 2000,62(16):10696.
[46]S. Foteinopoulou, C. Soukoulis. Negative refraction and left-handed behavior in two-dimensional photonic crystals[J]. Phys Rev B,2003,67(23):235107.
[47]S. John. Strong localization of photons in certain disordered dielectric superlattices[J]. Phys Rev Lett,1987,58(23):2486-2489.
[48]E. Yablonovitch. Inhibited spontaneous emission in solid-state physics and electronics[J]. Phys Rev Lett,1987,58(20):2059-2062.
[49]J. D. Joannopoulos, Photonic crystals:molding the flow of light. Second Edition ed. New Jersey:Princeton University,2008.
[50]C. Luo, S. G. Johnson, J. Joannopoulos, et al. All-angle negative refraction without negative effective index [J]. Phys Rev B,2002,65(20):201104.
[51]P. V. Parimi, W. T. Lu, P. Vodo, et al. Negative refraction and left-handed electromagnetism in microwave photonic crystals[J]. Phys Rev Lett,2004,92(12): 127401.
[52]A. Berrier, M. Mulot, M. Swillo, et al. Negative refraction at infrared wavelengths in a two-dimensional photonic crystal[J]. Phys Rev Lett, 2004,93(7): 073902.
[53]E. Cubukcu, K. Aydin, E. Ozbay, et al. Electromagnetic waves:Negative refraction by photonic crystals[J]. Nature,2003,423:604-605.
[54]P. V. Parimi, W. T. Lu, P. Vodo, et al. Photonic crystals:imaging by flat lens using negative refraction[J]. Nature,2003,426:404.
[55]S. Zhang, W. Fan, N. C. Panoiu, et al. Experimental demonstration of near-infrared negative-index metamaterials[J]. Phys Rev Lett,2005,95(13): 137404.
[56]G. Dolling, C. Enkrich, M. Wegener, et al. Low-loss negative-index metamaterial at telecommunication wavelengths[J]. Opt Lett, 2006, 31(12): 1800-1802.
[57]S. Zhang, W. Fan, K. Malloy, et al. Demonstration of metal-dielectric negative-index metamaterials with improved performance at optical frequencies [J]. J Opt Soc Am B,2006,23(3):434-438.
[58]D. R. Smith, D. Schurig. Electromagnetic wave propagation in media with indefinite permittivity and permeability tensors[J]. Phys Rev Lett, 2003,90(7): 77405.
[59]P. A. Belov. Backward waves and negative refraction in uniaxial dielectrics with negative dielectric permittivity along the anisotropy axis[J]. Microwave and Optical Technology Letters,2003,37(4):259-263.
[60]A. J. Hoffman, L. Alekseyev, S.S. Howard, et al. Negative refraction in semiconductor metamaterials[J]. Nat Mater,2007,6(12):946-50.
[61]B. Wood, J. Pendry, D. Tsai. Directed subwavelength imaging using a layered metal-dielectric system[J]. Phys Rev B,2006,74(11):115116.
[62]A. P. Viktor, K. S. Andrey, M. S. Vladimir. Plasmon modes and negative refraction in metal nanowire composites [J]. Opt Exp,2003,11(7):735-745.
[63]W. Robyn, E. Justin, E. N. Evgenii, et al. Nonmagnetic nanocomposites for optical and infrared negative-refractive-index media[J]. J. Opt. Soc. Am. B,2006, 23(3):498-505.
[64]J. Yao, Z. Liu, Y. Liu, et al. Optical Negative Refraction in Bulk Metamaterials of Nanowires[J]. Science,2008,321:930.
[65]Y. Liu, G. Bartall, X. Zhang, et al. All-angle negative refraction and imaging in a bulk medium made of metallic nanowires in the visible region [J]. Opt Exp, 2008,16(20):15439-15448.
[66]X. Ao, S. He. Negative refraction of left-handed behavior in porous alumina with infiltrated silver at an optical wavelength[J]. Appl Phys Lett,2005,87(10): 101112.
[67]Y. Zhang,, B. Fluegel, A. Mascarenhas. Total negative refraction in real crystals for ballistic electrons and light[J]. Phys Rev Lett,2003,91(15):157404.
[68]X. Chen, M. He, Y. Du, et al. Negative refraction:an intrinsic property of uniaxial crystals[J]. Phys Rev B,2005,72(11):113111.
[69]O. P. Pishnyak, O.D. Lavrentovich. Electrically controlled negative refraction in a nematic liquid crystal[J]. Appl Phys Lett,2006,89(25):251103.
[70]Q. Zhao, L. Kang, B. Li, et al. Tunable negative refraction in nematic liquid crystals[J]. Appl Phys Lett,2006,89(22):221918.
[71]L. Kang, Q. Zhao, B. Li, et al. Experimental verification of a tunable optical negative refraction in nematic liquid crystals[J]. Appl Phys Lett,2007,90(18): 191831.
[72]Q. Zhao, J. Zhou, F. Zhang, et al. Mie resonance-based dielectric metamaterials[J]. Materials,2009,12(12):60-69.
[73]W. T. Doyle, Optical properties of a suspension of metal spheres[J]. Phys Rev B, 1989,39(14):9852-9858.
[74]H. Hovel, S. Fritz, A. Hilger, et al. Width of Cluster Plasmon Resonances-Bulk Dielectric Functions and Chemical Interface Damping[J]. Phys Rev B,1993, 48(24):18178-18188.
[75]M. M. Alvarez, J. T. Khoury, T. G. Schaaff, et al. Optical absorption spectra of nanocrystal gold molecules[J]. J Phys Chem B,1997,101(19):3706-3712.
[76]B. Palpant, B. Prevel, J. Lerme, et al. Optical properties of gold clusters in the size range 2-4 nm[J]. Phys Rev B,1998,57(3):1963-1970.
[77]M. Wheeler, J. Aitchison, M. Mojahedi. Three-dimensional array of dielectric spheres with an isotropic negative permeability at infrared frequencies[J]. Phys Rev B,2005,72:193103.
[78]M. Wheeler, J. Aitchison, M. Mojahedi. Coated nonmagnetic spheres with a negative index of refraction at infrared frequencies [J]. Phys Rev B,2006,73: 045105.
[79]M. Born, E. Wolf. Principles of Optics:Electromagnetic Theory of Propagation, Interference and Diffraction of Light[M]. Seventh Edition ed. London:Cambridge University Press,2002.
[80]马科斯.波恩,埃米尔.沃耳夫.光学原理第七版[M].北京：电子工业出版社,2007年.
[81]C. Wenshan, S. Vladimir. Optical Metamaterials[M]. New York:Springer Science+Business Media, LLC,2010.
[82]A. D. Rakic, A. B. Djurisic, J. M. Elazar, et al. Optical properties of metallic films for vertical-cavity optoelectronic devices[J]. Appl Opt,1998,37(22): 5271-5283.
[83]S. Gauza, C.H. Wen, S.T. Wu, et al. Super high birefringence isothiocyanato biphenyl-bistolane liquid crystals[J]. Japanese journal of applied physics,2004, 43(11):7634-7638.
[84]J. Li, C.H. Wen, S. Gauza, et al. Refractive indices of liquid crystals for display applications[J]. Journal of Display Technology,2005,1(1):51-61.
[85]A. Yariv, P. Yeh. Optical waves in crystals:propagation and control of laser radiation[M]. New York:John Wiley&Sons,1984.
[86]E. Spinozzil, A. Ciattoni. Ultrathin optical switch based on a liquid crystal/silver nanoparticles mixture as a tunable indefinite medium[J]. Opt Mat Exp,1(4): 732-741.
[87]D. Demus, J. Goodby, G W. Gray, et al., Physical Properties of liquid crystals. New York:Wiley,1999.
[88]I.C Khoo, Liquid Crystals. Sencond edition. New York:Wiley,2007.
[89]S. Gauza, J. Li, S. T. Wu, et al. High birefringence and high resistivity isothiocyanate-based nematic liquid crystal mixtures[J]. Liquid Crystals,2005, 32(8):1077-1085.
[90]Y. M. Liao, H. L. Chen, C. S. Hsu, et al. Synthesis and mesomorphic properties of super high birefringence isothiocyanato bistolane liquid crystals [J]. Liquid Crystals,2007,34(4):507-517.
[91]A. B. Golovin, S. V. Shiyanovskii, O. D. Lavrentovich. Fast switching dual-frequency liquid crystal optical retarder, driven by an amplitude and frequency modulated voltage[J]. Appl phys lett,2003,83(19):3864-3866.
[92]A. Kirby, G Love. Fast, large and controllable phase modulation using dual frequency liquid crystals[J]. Opt Exp,2004,12(7):1470-1475.
[93]C. A. FOSS, J. G. L. Hornyak, J. A. Stockert, et al. Template-Synthesized Nanoscopic Gold Particles:Optical Spectra and the Effects of Particle Size and Shape[J]. J. Phys. Chem, 1994,98:2963-2971.
[94]P. B. Johnson, R. W. Christy. Optical constants of noble metals[J]. Phys Rev B, 1972,6(12):4370-4379.
[95]H. Masuda, K. Fukuda. Ordered metal nanohole arrays made by a two-step replication of honeycomb structures of anodic alumina[J]. Science,1995,268: 1466-1468.
[96]M. Adachi, D. J. Lockwood. Self-Organized Nanoscale Materials[J]. New York: Springer,2006.
[97]J. Kanungo, J. Schilling. Experimental determination of the principal dielectric functions in silver nanowire metamaterials[J]. Appl Phys Lett,2010,97:021903.
[98]L. Huang, H. Wang, Z. Wang, et al. Nanowire arrays electrodeposited from liquid crystalline phases[J]. Adv Mat,2002,14(1):61-64.
[99]A. M. F Neto, S. R. A. Salinas, et al. The physics of lyotropic liquid crystals. New York:Oxford Univerity Press,2005.
[100]P. Alexandridis, U. Olsson, B. Lindman, et al. A record nine different phases (four cubic, two hexagonal, and one lamellar lyotropic liquid crystalline and two micellar solutions) in a ternary isothermal system of an amphiphilic block copolymer and selective solvents (water and oil)[J]. Langmuir,1998,14(10): 2627-2638.
[101]P. Ekwall, L. Mandell, K. Fontell, et al. Solubilization in Micelles and Mesophases and Transition from Normal to Reversed Structures[J]. Molecular Crystals and Liquid Crystals,1969,8:157-213.