Three-dimensional optical metamaterial with a negative refractive index

Valentine, Jason and Zhang, Shuang and Zentgraf, Thomas and Ulin-Avila, Erick and Genov, Dentcho A. and Bartal, Guy and Zhang, Xiang. (2008) Three-dimensional optical metamaterial with a negative refractive index. Nature, 455 (7211). pp. 376-379. ISSN 0028-0836

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Abstract

Metamaterials are artificially engineered structures that have properties, such as a negative refractive index1, 2, 3, 4, not attainable with naturally occurring materials. Negative-index metamaterials (NIMs) were first demonstrated for microwave frequencies5, 6, but it has been challenging to design NIMs for optical frequencies and they have so far been limited to optically thin samples because of significant fabrication challenges and strong energy dissipation in metals7, 8. Such thin structures are analogous to a monolayer of atoms, making it difficult to assign bulk properties such as the index of refraction. Negative refraction of surface plasmons was recently demonstrated but was confined to a two-dimensional waveguide9. Three-dimensional (3D) optical metamaterials have come into focus recently, including the realization of negative refraction by using layered semiconductor metamaterials and a 3D magnetic metamaterial in the infrared frequencies; however, neither of these had a negative index of refraction10, 11. Here we report a 3D optical metamaterial having negative refractive index with a very high figure of merit of 3.5 (that is, low loss). This metamaterial is made of cascaded 'fishnet' structures, with a negative index existing over a broad spectral range. Moreover, it can readily be probed from free space, making it functional for optical devices. We construct a prism made of this optical NIM to demonstrate negative refractive index at optical frequencies, resulting unambiguously from the negative phase evolution of the wave propagating inside the metamaterial. Bulk optical metamaterials open up prospects for studies of 3D optical effects and applications associated with NIMs and zero-index materials such as reversed Doppler effect, superlenses, optical tunnelling devices12, 13, compact resonators and highly directional sources14.

Item Type: Article
Additional Information: Reprinted by permission from Macmillan Publishers Ltd: [Nature] ("Three-dimensional optical metamaterial with a negative refractive index", Valentine J. et al., Nature 455, 376-379). Copyright (2008).
Uncontrolled Keywords: Metamaterials, Negative index of refraction
InterNano Taxonomy: Nanoscale Objects and Nanostructured Materials > Nanocomposites > Optical
Collections: Nanomanufacturing Research Collection
Depositing User: Moureen Kemei
Date Deposited: 07 Apr 2010 19:25
Last Modified: 07 Apr 2010 19:25
URI: http://eprints.internano.org/id/eprint/414

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