最新左手材料LeftHandedMetamaterials及负折射率的研究进展课件PPT课件.ppt

左手材料左手材料LeftHandedMetamaterialsLeftHandedMetamaterials及负折射率的研究进展课件及负折射率的研究进展课件主要内容—什么是左手材料（Left-Handed Metama-terials)与负折射率—左手材料的研究与进展—负折射率的应用前景左手材料的研究与进展Veselago V.G. , Sov. Phys. Usp. ,1968,10,509&1968年Veselago对电磁波在介电常数和磁导率同时为负数的介质中的传播特点作过纯理论的研究 但自然界中没有发现和同时为负数的介质存在，所以他的研究结果在20世纪一直没有得到实验验证，人们对左手材料的兴趣也基本消失了1996-1999年 ， Pendry等 人 相 继 提 出 了 用 周 期 性 排 列 的 金属条和开口金属谐振环(Split-Ring Resonator)可以在微波波段产生负等效介电常数和负等效磁导率Pendry J.B. ,et al. , Phys. Rev. Lett. ,1996,76,4773Pendry J.B. ,et al. , IEEE Trans. Microwave Theo. and Tech. ,1999,47,2075&2000年，Smith等人将金属丝板和SRR板有规律地排列在一起，制作了世界上第一块等效介电常数和等效磁导率同时为负数的介质。

Smith D.R. ,Willie J. ,et al. , Phys. Rev. Lett. ,2000,84,4184左手材料的研究与进展&2003年，Parazzoli等人在实验和数值模拟上进一步验证了NIM中的Snell定律，为左手物质是否真实存在的争论暂时划下了一个句点 Parazzoli C. G. ,Greegor R. B. ,et al , Phys. Rev. Lett. ,2003,90,107401&2001年，Shelby等人首次在实验上证实了当电磁波斜入射到左手材料与右手材料的分界面时，折射波的方向与入射波的方向在分界面法线的同侧Shelby R. ,Smith D.R. ,et al ,Science ,2001,292,77负折射率的应用发展前景 负折射率材料可以用于平板透镜，光束控制，耦合器等方面v“完美透镜” (Perfect Lens)的概念与应用L传统透镜的分辨率限制(diffraction limit)： x~2/k= 这也是造成DVD读写密度限制和光刻电路密度限制的主要原因。

J左手材料制成的透镜，在合适的条件下，可以成为“完美透镜”，实现亚波长分辨率v“完美透镜”的局限与解决方法 虽然负折射率材料制成的“完美透镜”可以实现亚波长分辨率，但是实现“完美透镜”的条件是相当苛刻的目前还只能在微波区段实现负折射率，而且频率范围很窄它们都是对电磁波有较大的损耗，而且很难将尺寸制作到足够小以至于在光学频率下使用 光子晶体 (Photonic Crystals)Fig 11. Photonic Crystals: (a), (b) Holes-in-dielectric; (c) rods-in-air(c)光子晶体(PC)是由两种或两种以上的电介质材料周期性排列而成的人造材料，排列周期为波长量级，具有光电带隙，可以控制电磁波在其中的传播在一定条件下，它也可以表现出负折射率的现象Parimi P., Lu W., et al. ,Phy. Rev. Lett. ,2004,92,127401Fig 12 (a) Experimental setup (not to scale). (b) Propagation vectors for positive and negative refraction. (c) –(f ) Microwave electric field maps in the far field region. (c) Negative and (e) positive refraction by the metallic PC prism for the incident beam along Γ→K (incident angle 30 ). WF(wave front) with respect to refracting surface. (d) Negative refraction for the incident beam along Γ→ M (incidence angle 60). (f ) Positive refraction by a polystyrene prism. In all the field maps, approximate area of each field map is 43 × 40 cm2. 光子晶体的 “等效负折射率”可以由构成材料的电介质的介电常数和材料周期性来调整，而且在高频率下有着很低的电磁损耗，三维PC比较容易制成，因此PC比左手材料更容易实现红外和光学频率下的应用。

展望Ø 光刻蚀技术(photolithography)Ø 近场光学显微仪 (near-field optical microscopy)Ø 可选波长的滤光器 (wavelength-tunable filter)Ø 光学显示器 (optical displays) 新材料往往伴随着新现象和新技术的发展随着负折射率材料的发展，许多原有的技术将得到新的发展Fig 5. (A) A negative index metamaterial formed by SRRs and wires deposited on opposite sides lithographically on standard circuit board. The height of the structure is 1 cm. (B) The power detected as a function of angle in a Snell’s law experiment performed on a Teflon sample (blue curve) and a negative index sample (red curve).Shelby R. ,Smith D.R. ,et al ,Science ,2001,292,77Fig 6. Unit cell of the 901 HWD structure. The direction of propagation of the electromagnetic field is along the x axis, the electric field is oriented along the z axis, and the magnetic field is along the y axis. C=0.025 cm, D=0.030 cm, G=0.046 cm, H= 0.0254 cm, L= 0.33 cm, S= 0.263 cm, T= 17.0×10-4 cm, W= 0.025 cm, and V= 0.255 cm.Fig 7. Schematic of the setup used in the Snell’s law experiment showing the conical horn, lens, sample, and waveguide detector. The measurements were made in the focused and collimated mode at 33 and 66 cm away from the sample.Parazzoli C. G. ,Greegor R. B. ,et al , Phys. Rev. Lett. ,2003,90,107401Fig 8. Surface plot of measured normalized Ez(r,f ). Refracted peaks :by Teflon at 48.2(n=1.4) and is independent of frequency; by the NIM , however, at 12.6GHz,-30.6 (n=-1.0454) that are a function of the frequency..Fig 9. (a) Measured angular profile of the normalized Ez(r), at f =12.6 GHz for detector distances of 33 and 66 cm from the wedges. (b) Measured 33 cm data compared to simulated results at 33, 66, and 238 cm (100λ)from the wedges.Fig 10. Perfect lensing in action: (A) the far field and (B) the near field, translating the object into a perfect image. (C) Microwave experiments* demonstrate that subwavelength focusing is possible, limited only by losses in the system. (D) Measured data compared to the perfect results. Losses limit the resolution to less than perfect but better than the diffraction limit.CD* Grbic A. ,Eleftheriades G. , Phy. Rev. Lett. ,2004,92,117403mo－磁共振频率； mp－磁等离子化频率eo－电子共振频率； ep－电等离子化频率只要0< < p，、就可以同时为负数。