Abstract

A dual-disk ring (DDR) structure with broken symmetry and weakly dissipating material, silver, is proposed to achieve Fano resonance in visible wavelength range. Symmetry breaking of a metallic ring is realized by placing two disks inside the ring. The excitation of the Fano resonance is interpreted in terms of coupling of the ring and the dual-disk plasmonic modes. The potential of using an array of such DDR nano structures as a biochemical sensor is evaluated with the figure of merit (FOM). Based on our design and simulation, arrays with DDR structures are fabricated and the Fano resonance peak is observed in visible wavelength range of extinction spectra of individual silver DDR nanostructures.

© 2011 OSA

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  1. B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. 9(9), 707–715 (2010).
    [CrossRef] [PubMed]
  2. A. E. Miroshnichenko, S. Flach, and Y. S. Kivshar, “Fano resonances in nanoscale structures,” Rev. Mod. Phys. 82(3), 2257–2298 (2010).
    [CrossRef]
  3. F. Hao, P. Nordlander, Y. Sonnefraud, P. Van Dorpe, and S. A. Maier, “Tunability of subradiant dipolar and fano-type plasmon resonances in metallic ring/disk cavities: implications for nanoscale optical sensing,” ACS Nano 3(3), 643–652 (2009).
    [CrossRef] [PubMed]
  4. F. Hao, Y. Sonnefraud, P. Van Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. 8(11), 3983–3988 (2008).
    [CrossRef] [PubMed]
  5. G. H. Chan, J. Zhao, G. C. Schatz, and R. P. Van Duyne, “Localized surface plasmon resonance spectroscopy of triangular aluminum nanoparticles,” J. Phys. Chem. C 112(36), 13958–13963 (2008).
    [CrossRef]
  6. M. Rahmani, B. Lukiyanchuk, B. Ng, A. Tavakkoli K G, Y. F. Liew, and M. H. Hong, “Generation of pronounced Fano resonances and tuning of subwavelength spatial light distribution in plasmonic pentamers,” Opt. Express 19(6), 4949–4956 (2011).
    [CrossRef] [PubMed]
  7. M. Rahmani, T. Tahmasebi, Y. Lin, B. Lukiyanchuk, T. Y. F. Liew, and M. H. Hong, “Influence of plasmon destructive interferences on optical properties of gold planar quadrumers,” Nanotechnology 22(24), 245204 (2011).
    [CrossRef] [PubMed]
  8. S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. 10(7), 2694–2701 (2010).
    [CrossRef] [PubMed]
  9. J. F. Ho, B. Luk'yanchuk, and J. B. Zhang, “Tunable Fano resonances in silver-silica-silver multilayer nanoshells,” Appl. Phys., A Mater. Sci. Process. (to be published).
  10. L. J. Sherry, S. H. Chang, G. C. Schatz, R. P. Van Duyne, B. J. Wiley, and Y. N. Xia, “Localized surface plasmon resonance spectroscopy of single silver nanocubes,” Nano Lett. 5(10), 2034–2038 (2005).
    [CrossRef] [PubMed]

2011 (2)

M. Rahmani, B. Lukiyanchuk, B. Ng, A. Tavakkoli K G, Y. F. Liew, and M. H. Hong, “Generation of pronounced Fano resonances and tuning of subwavelength spatial light distribution in plasmonic pentamers,” Opt. Express 19(6), 4949–4956 (2011).
[CrossRef] [PubMed]

M. Rahmani, T. Tahmasebi, Y. Lin, B. Lukiyanchuk, T. Y. F. Liew, and M. H. Hong, “Influence of plasmon destructive interferences on optical properties of gold planar quadrumers,” Nanotechnology 22(24), 245204 (2011).
[CrossRef] [PubMed]

2010 (3)

S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. 10(7), 2694–2701 (2010).
[CrossRef] [PubMed]

B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. 9(9), 707–715 (2010).
[CrossRef] [PubMed]

A. E. Miroshnichenko, S. Flach, and Y. S. Kivshar, “Fano resonances in nanoscale structures,” Rev. Mod. Phys. 82(3), 2257–2298 (2010).
[CrossRef]

2009 (1)

F. Hao, P. Nordlander, Y. Sonnefraud, P. Van Dorpe, and S. A. Maier, “Tunability of subradiant dipolar and fano-type plasmon resonances in metallic ring/disk cavities: implications for nanoscale optical sensing,” ACS Nano 3(3), 643–652 (2009).
[CrossRef] [PubMed]

2008 (2)

F. Hao, Y. Sonnefraud, P. Van Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. 8(11), 3983–3988 (2008).
[CrossRef] [PubMed]

G. H. Chan, J. Zhao, G. C. Schatz, and R. P. Van Duyne, “Localized surface plasmon resonance spectroscopy of triangular aluminum nanoparticles,” J. Phys. Chem. C 112(36), 13958–13963 (2008).
[CrossRef]

2005 (1)

L. J. Sherry, S. H. Chang, G. C. Schatz, R. P. Van Duyne, B. J. Wiley, and Y. N. Xia, “Localized surface plasmon resonance spectroscopy of single silver nanocubes,” Nano Lett. 5(10), 2034–2038 (2005).
[CrossRef] [PubMed]

Bardhan, R.

S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. 10(7), 2694–2701 (2010).
[CrossRef] [PubMed]

Chan, G. H.

G. H. Chan, J. Zhao, G. C. Schatz, and R. P. Van Duyne, “Localized surface plasmon resonance spectroscopy of triangular aluminum nanoparticles,” J. Phys. Chem. C 112(36), 13958–13963 (2008).
[CrossRef]

Chang, S. H.

L. J. Sherry, S. H. Chang, G. C. Schatz, R. P. Van Duyne, B. J. Wiley, and Y. N. Xia, “Localized surface plasmon resonance spectroscopy of single silver nanocubes,” Nano Lett. 5(10), 2034–2038 (2005).
[CrossRef] [PubMed]

Chong, C. T.

B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. 9(9), 707–715 (2010).
[CrossRef] [PubMed]

Flach, S.

A. E. Miroshnichenko, S. Flach, and Y. S. Kivshar, “Fano resonances in nanoscale structures,” Rev. Mod. Phys. 82(3), 2257–2298 (2010).
[CrossRef]

Giessen, H.

B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. 9(9), 707–715 (2010).
[CrossRef] [PubMed]

Halas, N. J.

B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. 9(9), 707–715 (2010).
[CrossRef] [PubMed]

S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. 10(7), 2694–2701 (2010).
[CrossRef] [PubMed]

F. Hao, Y. Sonnefraud, P. Van Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. 8(11), 3983–3988 (2008).
[CrossRef] [PubMed]

Hao, F.

F. Hao, P. Nordlander, Y. Sonnefraud, P. Van Dorpe, and S. A. Maier, “Tunability of subradiant dipolar and fano-type plasmon resonances in metallic ring/disk cavities: implications for nanoscale optical sensing,” ACS Nano 3(3), 643–652 (2009).
[CrossRef] [PubMed]

F. Hao, Y. Sonnefraud, P. Van Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. 8(11), 3983–3988 (2008).
[CrossRef] [PubMed]

Ho, J. F.

J. F. Ho, B. Luk'yanchuk, and J. B. Zhang, “Tunable Fano resonances in silver-silica-silver multilayer nanoshells,” Appl. Phys., A Mater. Sci. Process. (to be published).

Hong, M. H.

M. Rahmani, B. Lukiyanchuk, B. Ng, A. Tavakkoli K G, Y. F. Liew, and M. H. Hong, “Generation of pronounced Fano resonances and tuning of subwavelength spatial light distribution in plasmonic pentamers,” Opt. Express 19(6), 4949–4956 (2011).
[CrossRef] [PubMed]

M. Rahmani, T. Tahmasebi, Y. Lin, B. Lukiyanchuk, T. Y. F. Liew, and M. H. Hong, “Influence of plasmon destructive interferences on optical properties of gold planar quadrumers,” Nanotechnology 22(24), 245204 (2011).
[CrossRef] [PubMed]

Kivshar, Y. S.

A. E. Miroshnichenko, S. Flach, and Y. S. Kivshar, “Fano resonances in nanoscale structures,” Rev. Mod. Phys. 82(3), 2257–2298 (2010).
[CrossRef]

Lassiter, J. B.

S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. 10(7), 2694–2701 (2010).
[CrossRef] [PubMed]

Liew, T. Y. F.

M. Rahmani, T. Tahmasebi, Y. Lin, B. Lukiyanchuk, T. Y. F. Liew, and M. H. Hong, “Influence of plasmon destructive interferences on optical properties of gold planar quadrumers,” Nanotechnology 22(24), 245204 (2011).
[CrossRef] [PubMed]

Liew, Y. F.

Lin, Y.

M. Rahmani, T. Tahmasebi, Y. Lin, B. Lukiyanchuk, T. Y. F. Liew, and M. H. Hong, “Influence of plasmon destructive interferences on optical properties of gold planar quadrumers,” Nanotechnology 22(24), 245204 (2011).
[CrossRef] [PubMed]

Luk’yanchuk, B.

B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. 9(9), 707–715 (2010).
[CrossRef] [PubMed]

Lukiyanchuk, B.

M. Rahmani, T. Tahmasebi, Y. Lin, B. Lukiyanchuk, T. Y. F. Liew, and M. H. Hong, “Influence of plasmon destructive interferences on optical properties of gold planar quadrumers,” Nanotechnology 22(24), 245204 (2011).
[CrossRef] [PubMed]

M. Rahmani, B. Lukiyanchuk, B. Ng, A. Tavakkoli K G, Y. F. Liew, and M. H. Hong, “Generation of pronounced Fano resonances and tuning of subwavelength spatial light distribution in plasmonic pentamers,” Opt. Express 19(6), 4949–4956 (2011).
[CrossRef] [PubMed]

Luk'yanchuk, B.

J. F. Ho, B. Luk'yanchuk, and J. B. Zhang, “Tunable Fano resonances in silver-silica-silver multilayer nanoshells,” Appl. Phys., A Mater. Sci. Process. (to be published).

Maier, S. A.

B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. 9(9), 707–715 (2010).
[CrossRef] [PubMed]

F. Hao, P. Nordlander, Y. Sonnefraud, P. Van Dorpe, and S. A. Maier, “Tunability of subradiant dipolar and fano-type plasmon resonances in metallic ring/disk cavities: implications for nanoscale optical sensing,” ACS Nano 3(3), 643–652 (2009).
[CrossRef] [PubMed]

F. Hao, Y. Sonnefraud, P. Van Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. 8(11), 3983–3988 (2008).
[CrossRef] [PubMed]

Miroshnichenko, A. E.

A. E. Miroshnichenko, S. Flach, and Y. S. Kivshar, “Fano resonances in nanoscale structures,” Rev. Mod. Phys. 82(3), 2257–2298 (2010).
[CrossRef]

Mukherjee, S.

S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. 10(7), 2694–2701 (2010).
[CrossRef] [PubMed]

Ng, B.

Nordlander, P.

S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. 10(7), 2694–2701 (2010).
[CrossRef] [PubMed]

B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. 9(9), 707–715 (2010).
[CrossRef] [PubMed]

F. Hao, P. Nordlander, Y. Sonnefraud, P. Van Dorpe, and S. A. Maier, “Tunability of subradiant dipolar and fano-type plasmon resonances in metallic ring/disk cavities: implications for nanoscale optical sensing,” ACS Nano 3(3), 643–652 (2009).
[CrossRef] [PubMed]

F. Hao, Y. Sonnefraud, P. Van Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. 8(11), 3983–3988 (2008).
[CrossRef] [PubMed]

Rahmani, M.

M. Rahmani, T. Tahmasebi, Y. Lin, B. Lukiyanchuk, T. Y. F. Liew, and M. H. Hong, “Influence of plasmon destructive interferences on optical properties of gold planar quadrumers,” Nanotechnology 22(24), 245204 (2011).
[CrossRef] [PubMed]

M. Rahmani, B. Lukiyanchuk, B. Ng, A. Tavakkoli K G, Y. F. Liew, and M. H. Hong, “Generation of pronounced Fano resonances and tuning of subwavelength spatial light distribution in plasmonic pentamers,” Opt. Express 19(6), 4949–4956 (2011).
[CrossRef] [PubMed]

Schatz, G. C.

G. H. Chan, J. Zhao, G. C. Schatz, and R. P. Van Duyne, “Localized surface plasmon resonance spectroscopy of triangular aluminum nanoparticles,” J. Phys. Chem. C 112(36), 13958–13963 (2008).
[CrossRef]

L. J. Sherry, S. H. Chang, G. C. Schatz, R. P. Van Duyne, B. J. Wiley, and Y. N. Xia, “Localized surface plasmon resonance spectroscopy of single silver nanocubes,” Nano Lett. 5(10), 2034–2038 (2005).
[CrossRef] [PubMed]

Sherry, L. J.

L. J. Sherry, S. H. Chang, G. C. Schatz, R. P. Van Duyne, B. J. Wiley, and Y. N. Xia, “Localized surface plasmon resonance spectroscopy of single silver nanocubes,” Nano Lett. 5(10), 2034–2038 (2005).
[CrossRef] [PubMed]

Sobhani, H.

S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. 10(7), 2694–2701 (2010).
[CrossRef] [PubMed]

Sonnefraud, Y.

F. Hao, P. Nordlander, Y. Sonnefraud, P. Van Dorpe, and S. A. Maier, “Tunability of subradiant dipolar and fano-type plasmon resonances in metallic ring/disk cavities: implications for nanoscale optical sensing,” ACS Nano 3(3), 643–652 (2009).
[CrossRef] [PubMed]

F. Hao, Y. Sonnefraud, P. Van Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. 8(11), 3983–3988 (2008).
[CrossRef] [PubMed]

Tahmasebi, T.

M. Rahmani, T. Tahmasebi, Y. Lin, B. Lukiyanchuk, T. Y. F. Liew, and M. H. Hong, “Influence of plasmon destructive interferences on optical properties of gold planar quadrumers,” Nanotechnology 22(24), 245204 (2011).
[CrossRef] [PubMed]

Tavakkoli K G, A.

Van Dorpe, P.

F. Hao, P. Nordlander, Y. Sonnefraud, P. Van Dorpe, and S. A. Maier, “Tunability of subradiant dipolar and fano-type plasmon resonances in metallic ring/disk cavities: implications for nanoscale optical sensing,” ACS Nano 3(3), 643–652 (2009).
[CrossRef] [PubMed]

F. Hao, Y. Sonnefraud, P. Van Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. 8(11), 3983–3988 (2008).
[CrossRef] [PubMed]

Van Duyne, R. P.

G. H. Chan, J. Zhao, G. C. Schatz, and R. P. Van Duyne, “Localized surface plasmon resonance spectroscopy of triangular aluminum nanoparticles,” J. Phys. Chem. C 112(36), 13958–13963 (2008).
[CrossRef]

L. J. Sherry, S. H. Chang, G. C. Schatz, R. P. Van Duyne, B. J. Wiley, and Y. N. Xia, “Localized surface plasmon resonance spectroscopy of single silver nanocubes,” Nano Lett. 5(10), 2034–2038 (2005).
[CrossRef] [PubMed]

Wiley, B. J.

L. J. Sherry, S. H. Chang, G. C. Schatz, R. P. Van Duyne, B. J. Wiley, and Y. N. Xia, “Localized surface plasmon resonance spectroscopy of single silver nanocubes,” Nano Lett. 5(10), 2034–2038 (2005).
[CrossRef] [PubMed]

Xia, Y. N.

L. J. Sherry, S. H. Chang, G. C. Schatz, R. P. Van Duyne, B. J. Wiley, and Y. N. Xia, “Localized surface plasmon resonance spectroscopy of single silver nanocubes,” Nano Lett. 5(10), 2034–2038 (2005).
[CrossRef] [PubMed]

Zhang, J. B.

J. F. Ho, B. Luk'yanchuk, and J. B. Zhang, “Tunable Fano resonances in silver-silica-silver multilayer nanoshells,” Appl. Phys., A Mater. Sci. Process. (to be published).

Zhao, J.

G. H. Chan, J. Zhao, G. C. Schatz, and R. P. Van Duyne, “Localized surface plasmon resonance spectroscopy of triangular aluminum nanoparticles,” J. Phys. Chem. C 112(36), 13958–13963 (2008).
[CrossRef]

Zheludev, N. I.

B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. 9(9), 707–715 (2010).
[CrossRef] [PubMed]

ACS Nano (1)

F. Hao, P. Nordlander, Y. Sonnefraud, P. Van Dorpe, and S. A. Maier, “Tunability of subradiant dipolar and fano-type plasmon resonances in metallic ring/disk cavities: implications for nanoscale optical sensing,” ACS Nano 3(3), 643–652 (2009).
[CrossRef] [PubMed]

Appl. Phys., A Mater. Sci. Process. (1)

J. F. Ho, B. Luk'yanchuk, and J. B. Zhang, “Tunable Fano resonances in silver-silica-silver multilayer nanoshells,” Appl. Phys., A Mater. Sci. Process. (to be published).

J. Phys. Chem. C (1)

G. H. Chan, J. Zhao, G. C. Schatz, and R. P. Van Duyne, “Localized surface plasmon resonance spectroscopy of triangular aluminum nanoparticles,” J. Phys. Chem. C 112(36), 13958–13963 (2008).
[CrossRef]

Nano Lett. (3)

S. Mukherjee, H. Sobhani, J. B. Lassiter, R. Bardhan, P. Nordlander, and N. J. Halas, “Fanoshells: nanoparticles with built-in Fano resonances,” Nano Lett. 10(7), 2694–2701 (2010).
[CrossRef] [PubMed]

F. Hao, Y. Sonnefraud, P. Van Dorpe, S. A. Maier, N. J. Halas, and P. Nordlander, “Symmetry breaking in plasmonic nanocavities: subradiant LSPR sensing and a tunable Fano resonance,” Nano Lett. 8(11), 3983–3988 (2008).
[CrossRef] [PubMed]

L. J. Sherry, S. H. Chang, G. C. Schatz, R. P. Van Duyne, B. J. Wiley, and Y. N. Xia, “Localized surface plasmon resonance spectroscopy of single silver nanocubes,” Nano Lett. 5(10), 2034–2038 (2005).
[CrossRef] [PubMed]

Nanotechnology (1)

M. Rahmani, T. Tahmasebi, Y. Lin, B. Lukiyanchuk, T. Y. F. Liew, and M. H. Hong, “Influence of plasmon destructive interferences on optical properties of gold planar quadrumers,” Nanotechnology 22(24), 245204 (2011).
[CrossRef] [PubMed]

Nat. Mater. (1)

B. Luk’yanchuk, N. I. Zheludev, S. A. Maier, N. J. Halas, P. Nordlander, H. Giessen, and C. T. Chong, “The Fano resonance in plasmonic nanostructures and metamaterials,” Nat. Mater. 9(9), 707–715 (2010).
[CrossRef] [PubMed]

Opt. Express (1)

Rev. Mod. Phys. (1)

A. E. Miroshnichenko, S. Flach, and Y. S. Kivshar, “Fano resonances in nanoscale structures,” Rev. Mod. Phys. 82(3), 2257–2298 (2010).
[CrossRef]

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Figures (6)

Fig. 1
Fig. 1

(a) Schematic 3D illustration of the dual-disk ring (DDR) nanostructure (b) 2D layout of DDR with geometric parameters.

Fig. 2
Fig. 2

(a) Extinction spectrum for sliver (Ag) dual-disk ring (DDR) on a silica substrate with r1 = 146 nm, r2 = 120 nm, R = 44 nm and g = 10 nm; (b) The left electric field distribution at the wavelength of 557 nm represents the anti-bonding mode combining of ring dipole and disk dipole; the middle plot at the wavelength of 684 nm represents the coupling of ring octupolar mode and disks dipole mode, resulting in a Fano resonance; the right at the wavelength of 1589 nm represents the bonding mode from the ring dipole and the disk dipole.

Fig. 3
Fig. 3

Extinction spectra for sliver (Ag) dual-disk ring (DDR) structures (a) with r1 = 146 nm, r2 = 120 nm, R = 44 nm and n = 1 as a function of the gap for: g = 6 nm, 10 nm and 14 nm; (b) with r1 = 146 nm, r2 = 120 nm, and g = 10 nm as a function of the disk size R for: R = 44 nm, 48 nm and 52 nm; (c) with r2 = 120 nm, R = 44 nm, and g = 10 nm as a function of ring outer radius r1 for: r1 = 146 nm, 140 nm and 134 nm; (d) with r1 = 146 nm, r2 = 120 nm, R = 44 nm and g = 10 nm as a function of irradiation polarization along: x-axis (the axis passing through the centers of the two disks) polarization and y-axis polarization. Inset: electric field distribution for Fano resonance peak with the irradiation light at x and y polarizations respectively.

Fig. 4
Fig. 4

Refractive index sensitivity for dual-disk ring (DDR) structures. (a) Spectra of structures with r1 = 146 nm, r2 = 120 nm, R = 44 nm and g = 10 nm for surrounding media with different refractive index, at n = 1, 1.25 and 1.33. Inset: wavelength shift of the Fano resonance peaks for surrounding media with different refractive index at gaps of 6 nm, 10 nm and 14 nm. (b) Spectra of structures with r1 = 146 nm, r2 = 120 nm, R = 44 nm and g = 10 nm, as a function of the thickness of an additional dielectric coating, at 0 nm, 2 nm and 4 nm respectively. The upper inset depicts the manner of the dielectric capping layer binding onto the top surface and the side wall of a nanodisk and the lower inset depicts a bare nanodisk (equivalent to a capping layer with zero thickness).

Fig. 5
Fig. 5

(a) A scanning electron microscopy (SEM) image of Electron beam lithography (EBL) fabricated array and a close view of one representative dual-disk ring (DDR) structure on quartz substrate with controlled geometry of, in this case, r1 = 146 nm, r2 = 120 nm, R = 44 nm and g = 10 nm. (b) True color charged coupled device (CCD) images of DDR structures with r1 = 147 nm, r2 = 133 nm, and (I) R = 40 nm, g = 10, (II) R = 40 nm, g = 15 nm, (III) R = 43 nm, g = 15 nm, (IV) R = 38 nm, g = 15 nm, respectively.

Fig. 6
Fig. 6

(a) Simulated extinction spectrum of a single Ag Dual-Disk Ring (DDR) nanostructure with r1 = 175 nm, r2 = 130 nm, R = 54 nm and g = 15 nm. (b) Measured scattering spectrum of a single Ag DDR with the same dimensions used in the simulation.

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