3D metamaterials: Erected U-shaped nano-rings and plasmonic toroidal metamaterials at optical frequencies

Chen, W.T., Wu, P.C., Huang, Y.W., Hsiao, C.T., Yang, K.-Y., Liao, C.Y., Fedotov, V., Savinov, Vassili, Zheludev, N.I. and Tsai, D.P. (2012) 3D metamaterials: Erected U-shaped nano-rings and plasmonic toroidal metamaterials at optical frequencies. E-MRS '12 Symposium on Control of light at the nanoscale:materials, techniques and applications, Strasbourg, France. 13 - 17 May 2012.

Abstract

Split ring resonators (SRRs) were shown to exhibit electric and magnetic resonances from micro wave to visible light region in the past decade. Owing to the fabrication challenge, so far most SRRs structures were fabricated in planar type, i.e. SRRs laying on a supporting substrate. Here we fabricate the three-dimensional meta-molecule consisted of an array of erected SRRs structure and investigate the plasmonic resonance modes both by finite-element simulations and optical measurements, which are in excellent agreement with each other [1]. Using the double exposure electron beam lithography process with precise alignment technique (under 10 nm misalignment), the erected U-shape gold SRRs structures were fabricated on a glass substrate to study the plasmonic resonant modes of three dimensional metamaterials. We find electromagnetic field can be enhanced either between two prongs oraround two prongs of the erected U-shaped gold nano-rings corresponding to different plasmonic modes. The electromagnetic interaction of arranging four three-dimensional SRRs also results in extraordinary electromagnetic properties, such as toroidal dipole response [2]. The plasmonic toroidal spectral responses of solenoid-like toroidal metamolecule integrated by four erected U-shaped gold nano-rings at optical frequencies are experimentally and numerically studied at optical frequencies [3]. We propose a physical model based on coupled LC circuits to quantitatively analyze the coupled system and energy splitting of the plasmonic toroidal metamaterials. The gain-assistant optical spectra for toroidal resonance are also studied. These research results have potential to be applied in the area such as integrated photonic circuit, plasmonic biosensor and toroidal lasing spaser in optical frequency region.

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Contributors

Author: Vassili Savinov

Author: N.I. Zheludev

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