Abstract

We demonstrate an experimental method to separately test the optical response of a single sub-wavelength nano-structure to tailored electric and magnetic field distributions in the optical domain. For this purpose a highly focused y-polarized TEM10-mode is used which exhibits spatially separated longitudinal magnetic and transverse electric field patterns. By displacing a single sub-wavelength nano-structure, namely a single split-ring resonator (SRR), in the focal plane, different coupling scenarios can be achieved. It is shown experimentally that the single split-ring resonator tested here responds dominantly as an electric dipole. A much smaller but yet statistically significant magnetic dipole contribution is also measured by investigating the interaction of a single SRR with a magnetic field component perpendicular to the SRR plane (which is equivalent to the curl of the electric field) as well as by analyzing the intensity and polarization distribution of the scattered light with high spatial resolution. The developed experimental setup as well as the measurement techniques presented in this paper are a versatile tool to investigate the optical properties of single sub-wavelength nano-structures.

© 2010 Optical Society of America

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    [CrossRef] [PubMed]
  2. S. Quabis, R. Dorn, M. Eberler, O. Glöckl, and G. Leuchs, “Focusing light to a tighter spot,” Opt. Commun. 179, 1 (2000).
    [CrossRef]
  3. K. S. Youngworth, and T. G. Brown, “Focusing of high numerical aperture cylindrical vector beams,” Opt. Express 7, 77–87 (2000).
    [CrossRef] [PubMed]
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  5. R. Dorn, S. Quabis, and G. Leuchs, “Sharper Focus for a radially polarized light beam,” Phys. Rev. Lett. 91, 233901 (2003).
    [CrossRef] [PubMed]
  6. N. Huse, A. Schönle, and S. W. Hell, “Z-polarized confocal microscopy,” J. Biomed. Opt. 6, 273–276 (2001).
    [CrossRef] [PubMed]
  7. Q. Zhan, “Trapping metallic Rayleigh particles with radial polarization,” Opt. Express 12, 3377–3382 (2004).
    [CrossRef] [PubMed]
  8. M. Meier, V. Romano, and T. Feurer, “Material processing with pulsed radially and azimuthally polarized laser radiation,” Appl. Phys., A Mater. Sci. Process. 86, 329–334 (2007).
    [CrossRef]
  9. B. Sick, B. Hecht, U. P. Wild, and L. Novotny, “Probing confined fields with single molecules and vice versa,” J. Microsc. 202, 365–373 (2000).
    [CrossRef]
  10. L. Novotny, M. R. Beversluis, K. S. Youngworth, and T. G. Brown, “Longitudinal Field Modes Probed by Single Molecules,” Phys. Rev. Lett. 23, 5251–5254 (2001).
    [CrossRef]
  11. M. Lassen, G. Leuchs, and U. L. Andersen, “Continuous Variable Entanglement and Squeezing of Orbital Angular Momentum States,” Phys. Rev. Lett. 102, 163602 (2009).
    [CrossRef] [PubMed]
  12. J. Janousek, K. Wagner, J. F. Morizur, N. Treps, P. K. Lam, C. C. Harb, and H. A. Bachor, “Optical entanglement of co-propagating modes,” Nat. Photonics 3, 399–402 (2009).
    [CrossRef]
  13. J. Kindler, P. Banzer, S. Quabis, U. Peschel, and G. Leuchs, “Waveguide properties of single subwavelength holes demonstrated with radially and azimuthally polarized light,” Appl. Phys. B 89, 517–520 (2007).
    [CrossRef]
  14. A. V. Failla, S. Jäger, T. Züchner, M. Steiner, and A. J. Meixner, “Topology measurements of metal nanoparticles with 1 nm accuracy by Confocal Interference Scattering Microscopy,” Opt. Express 15, 8532–8542 (2007).
    [CrossRef] [PubMed]
  15. T. Züchner, and A. V. Failla, A. Hartschuh, and A. J. Meixner, “A novel approach to detect and characterize the scattering patterns of single Au nanoparticles using confocal microscopy,” J. Microsc. 29, 337–343 (2008).
    [CrossRef]
  16. J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic and electric excitations in split ring resonators,” Opt. Express 15, 17881–17890 (2007).
    [CrossRef] [PubMed]
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    [CrossRef]
  18. S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
    [CrossRef]
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    [CrossRef]
  20. M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, “Probing the Magnetic Field of Light at Optical Frequencies,” Science 23, 550–553 (2009).
    [CrossRef]
  21. C. Rockstuhl, F. Lederer, C. Etrich, T. Zentgraf, J. Kuhl, and H. Giessen, “On the reinterpretation of resonances in split-ring-resonators at normal incidence,” Opt. Express 14, 8827–8836 (2006).
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  23. R. Dorn, S. Quabis, and G. Leuchs, “The focus of light – linear polarization breaks the rotational symmetry of the focal spot,” J. Mod. Opt. 50, 1917–1926 (2003).
  24. C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
    [CrossRef]
  25. M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
    [CrossRef]
  26. S. Linden, C. Enkrich, M. Wegener, J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic response of metamaterials at 100 THz,” Science 306, 1351–1353 (2004).
    [CrossRef] [PubMed]
  27. L. Novotny, R. D. Grober, and K. Karrai, “Reflected image of a strongly focused spot,” Opt. Lett. 26, 789–791 (2001).
    [CrossRef]
  28. P. R. Bevington, and K. D. Robinson, in Data Reduction and Error Analysis for the Physical Sciences, McGraw-Hill Inc., US, 2002, 3rd Ed.
  29. Bi,norm = Bi/Ni with Ni = ? ?A(x0,y0)(?0/2 (|Ex|2 + |Ey|2))dxdy, Bi: maximum observed response derived from the line scan measurements, A(x0,y0): area of the SRR (metal area) centered at (x0,y0), and i = l, nl (l: SRR positioned in one of the main lobes; nl: SRR positioned on the nodal line).
  30. We are still investigating the explanation for the observed diagonal asymmetry. We already have evidence, that the asymmetry is a interference between the light reflected by the substrate and the electric as well as the magnetic dipole emission. Provided the SRR is not positioned exactly on the optical axis or is a result of the non-perfect shape of the SRR.

2009 (3)

M. Lassen, G. Leuchs, and U. L. Andersen, “Continuous Variable Entanglement and Squeezing of Orbital Angular Momentum States,” Phys. Rev. Lett. 102, 163602 (2009).
[CrossRef] [PubMed]

J. Janousek, K. Wagner, J. F. Morizur, N. Treps, P. K. Lam, C. C. Harb, and H. A. Bachor, “Optical entanglement of co-propagating modes,” Nat. Photonics 3, 399–402 (2009).
[CrossRef]

M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, “Probing the Magnetic Field of Light at Optical Frequencies,” Science 23, 550–553 (2009).
[CrossRef]

2008 (2)

T. Züchner, and A. V. Failla, A. Hartschuh, and A. J. Meixner, “A novel approach to detect and characterize the scattering patterns of single Au nanoparticles using confocal microscopy,” J. Microsc. 29, 337–343 (2008).
[CrossRef]

M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
[CrossRef]

2007 (4)

A. V. Failla, S. Jäger, T. Züchner, M. Steiner, and A. J. Meixner, “Topology measurements of metal nanoparticles with 1 nm accuracy by Confocal Interference Scattering Microscopy,” Opt. Express 15, 8532–8542 (2007).
[CrossRef] [PubMed]

J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic and electric excitations in split ring resonators,” Opt. Express 15, 17881–17890 (2007).
[CrossRef] [PubMed]

J. Kindler, P. Banzer, S. Quabis, U. Peschel, and G. Leuchs, “Waveguide properties of single subwavelength holes demonstrated with radially and azimuthally polarized light,” Appl. Phys. B 89, 517–520 (2007).
[CrossRef]

M. Meier, V. Romano, and T. Feurer, “Material processing with pulsed radially and azimuthally polarized laser radiation,” Appl. Phys., A Mater. Sci. Process. 86, 329–334 (2007).
[CrossRef]

2006 (2)

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

C. Rockstuhl, F. Lederer, C. Etrich, T. Zentgraf, J. Kuhl, and H. Giessen, “On the reinterpretation of resonances in split-ring-resonators at normal incidence,” Opt. Express 14, 8827–8836 (2006).
[CrossRef] [PubMed]

2005 (2)

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
[CrossRef]

2004 (3)

N. Katsarakis, T. Koschny, M. Kafesaki, E. N. Economou, and C. M. Soukoulis, “Electric coupling to the magnetic resonance of split ring resonators,” Appl. Phys. Lett. 84, 2943–2945 (2004).
[CrossRef]

Q. Zhan, “Trapping metallic Rayleigh particles with radial polarization,” Opt. Express 12, 3377–3382 (2004).
[CrossRef] [PubMed]

S. Linden, C. Enkrich, M. Wegener, J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic response of metamaterials at 100 THz,” Science 306, 1351–1353 (2004).
[CrossRef] [PubMed]

2003 (2)

R. Dorn, S. Quabis, and G. Leuchs, “The focus of light – linear polarization breaks the rotational symmetry of the focal spot,” J. Mod. Opt. 50, 1917–1926 (2003).

R. Dorn, S. Quabis, and G. Leuchs, “Sharper Focus for a radially polarized light beam,” Phys. Rev. Lett. 91, 233901 (2003).
[CrossRef] [PubMed]

2002 (1)

2001 (3)

L. Novotny, R. D. Grober, and K. Karrai, “Reflected image of a strongly focused spot,” Opt. Lett. 26, 789–791 (2001).
[CrossRef]

N. Huse, A. Schönle, and S. W. Hell, “Z-polarized confocal microscopy,” J. Biomed. Opt. 6, 273–276 (2001).
[CrossRef] [PubMed]

L. Novotny, M. R. Beversluis, K. S. Youngworth, and T. G. Brown, “Longitudinal Field Modes Probed by Single Molecules,” Phys. Rev. Lett. 23, 5251–5254 (2001).
[CrossRef]

2000 (3)

B. Sick, B. Hecht, U. P. Wild, and L. Novotny, “Probing confined fields with single molecules and vice versa,” J. Microsc. 202, 365–373 (2000).
[CrossRef]

S. Quabis, R. Dorn, M. Eberler, O. Glöckl, and G. Leuchs, “Focusing light to a tighter spot,” Opt. Commun. 179, 1 (2000).
[CrossRef]

K. S. Youngworth, and T. G. Brown, “Focusing of high numerical aperture cylindrical vector beams,” Opt. Express 7, 77–87 (2000).
[CrossRef] [PubMed]

1996 (1)

1991 (1)

M. O. Scully, and M. S. Zubairy, “Simple laser accelerator: Optics and particle dynamics,” Phys. Rev. A 44, 2656–2663 (1991).
[CrossRef] [PubMed]

Andersen, U. L.

M. Lassen, G. Leuchs, and U. L. Andersen, “Continuous Variable Entanglement and Squeezing of Orbital Angular Momentum States,” Phys. Rev. Lett. 102, 163602 (2009).
[CrossRef] [PubMed]

Bachor, H. A.

J. Janousek, K. Wagner, J. F. Morizur, N. Treps, P. K. Lam, C. C. Harb, and H. A. Bachor, “Optical entanglement of co-propagating modes,” Nat. Photonics 3, 399–402 (2009).
[CrossRef]

Banzer, P.

J. Kindler, P. Banzer, S. Quabis, U. Peschel, and G. Leuchs, “Waveguide properties of single subwavelength holes demonstrated with radially and azimuthally polarized light,” Appl. Phys. B 89, 517–520 (2007).
[CrossRef]

Beversluis, M. R.

L. Novotny, M. R. Beversluis, K. S. Youngworth, and T. G. Brown, “Longitudinal Field Modes Probed by Single Molecules,” Phys. Rev. Lett. 23, 5251–5254 (2001).
[CrossRef]

Brown, T. G.

L. Novotny, M. R. Beversluis, K. S. Youngworth, and T. G. Brown, “Longitudinal Field Modes Probed by Single Molecules,” Phys. Rev. Lett. 23, 5251–5254 (2001).
[CrossRef]

K. S. Youngworth, and T. G. Brown, “Focusing of high numerical aperture cylindrical vector beams,” Opt. Express 7, 77–87 (2000).
[CrossRef] [PubMed]

Burger, S.

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

Burresi, M.

M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, “Probing the Magnetic Field of Light at Optical Frequencies,” Science 23, 550–553 (2009).
[CrossRef]

Busch, K.

M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
[CrossRef]

Dolling, G.

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

Dorn, R.

R. Dorn, S. Quabis, and G. Leuchs, “Sharper Focus for a radially polarized light beam,” Phys. Rev. Lett. 91, 233901 (2003).
[CrossRef] [PubMed]

R. Dorn, S. Quabis, and G. Leuchs, “The focus of light – linear polarization breaks the rotational symmetry of the focal spot,” J. Mod. Opt. 50, 1917–1926 (2003).

S. Quabis, R. Dorn, M. Eberler, O. Glöckl, and G. Leuchs, “Focusing light to a tighter spot,” Opt. Commun. 179, 1 (2000).
[CrossRef]

Eberler, M.

S. Quabis, R. Dorn, M. Eberler, O. Glöckl, and G. Leuchs, “Focusing light to a tighter spot,” Opt. Commun. 179, 1 (2000).
[CrossRef]

Economou, E. N.

N. Katsarakis, T. Koschny, M. Kafesaki, E. N. Economou, and C. M. Soukoulis, “Electric coupling to the magnetic resonance of split ring resonators,” Appl. Phys. Lett. 84, 2943–2945 (2004).
[CrossRef]

Enkrich, C.

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
[CrossRef]

S. Linden, C. Enkrich, M. Wegener, J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic response of metamaterials at 100 THz,” Science 306, 1351–1353 (2004).
[CrossRef] [PubMed]

Etrich, C.

Failla, A. V.

T. Züchner, and A. V. Failla, A. Hartschuh, and A. J. Meixner, “A novel approach to detect and characterize the scattering patterns of single Au nanoparticles using confocal microscopy,” J. Microsc. 29, 337–343 (2008).
[CrossRef]

A. V. Failla, S. Jäger, T. Züchner, M. Steiner, and A. J. Meixner, “Topology measurements of metal nanoparticles with 1 nm accuracy by Confocal Interference Scattering Microscopy,” Opt. Express 15, 8532–8542 (2007).
[CrossRef] [PubMed]

Feth, N.

M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
[CrossRef]

Feurer, T.

M. Meier, V. Romano, and T. Feurer, “Material processing with pulsed radially and azimuthally polarized laser radiation,” Appl. Phys., A Mater. Sci. Process. 86, 329–334 (2007).
[CrossRef]

Gerthsen, D.

C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
[CrossRef]

Giessen, H.

Glöckl, O.

S. Quabis, R. Dorn, M. Eberler, O. Glöckl, and G. Leuchs, “Focusing light to a tighter spot,” Opt. Commun. 179, 1 (2000).
[CrossRef]

Grober, R. D.

Harb, C. C.

J. Janousek, K. Wagner, J. F. Morizur, N. Treps, P. K. Lam, C. C. Harb, and H. A. Bachor, “Optical entanglement of co-propagating modes,” Nat. Photonics 3, 399–402 (2009).
[CrossRef]

Hartschuh, A.

T. Züchner, and A. V. Failla, A. Hartschuh, and A. J. Meixner, “A novel approach to detect and characterize the scattering patterns of single Au nanoparticles using confocal microscopy,” J. Microsc. 29, 337–343 (2008).
[CrossRef]

Hecht, B.

B. Sick, B. Hecht, U. P. Wild, and L. Novotny, “Probing confined fields with single molecules and vice versa,” J. Microsc. 202, 365–373 (2000).
[CrossRef]

Heideman, R.

M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, “Probing the Magnetic Field of Light at Optical Frequencies,” Science 23, 550–553 (2009).
[CrossRef]

Hell, S. W.

N. Huse, A. Schönle, and S. W. Hell, “Z-polarized confocal microscopy,” J. Biomed. Opt. 6, 273–276 (2001).
[CrossRef] [PubMed]

Huse, N.

N. Huse, A. Schönle, and S. W. Hell, “Z-polarized confocal microscopy,” J. Biomed. Opt. 6, 273–276 (2001).
[CrossRef] [PubMed]

Husnik, M.

M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
[CrossRef]

Jäger, S.

Janousek, J.

J. Janousek, K. Wagner, J. F. Morizur, N. Treps, P. K. Lam, C. C. Harb, and H. A. Bachor, “Optical entanglement of co-propagating modes,” Nat. Photonics 3, 399–402 (2009).
[CrossRef]

Kafesaki, M.

N. Katsarakis, T. Koschny, M. Kafesaki, E. N. Economou, and C. M. Soukoulis, “Electric coupling to the magnetic resonance of split ring resonators,” Appl. Phys. Lett. 84, 2943–2945 (2004).
[CrossRef]

Kampfrath, T.

M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, “Probing the Magnetic Field of Light at Optical Frequencies,” Science 23, 550–553 (2009).
[CrossRef]

Karrai, K.

Katsarakis, N.

N. Katsarakis, T. Koschny, M. Kafesaki, E. N. Economou, and C. M. Soukoulis, “Electric coupling to the magnetic resonance of split ring resonators,” Appl. Phys. Lett. 84, 2943–2945 (2004).
[CrossRef]

Kindler, J.

J. Kindler, P. Banzer, S. Quabis, U. Peschel, and G. Leuchs, “Waveguide properties of single subwavelength holes demonstrated with radially and azimuthally polarized light,” Appl. Phys. B 89, 517–520 (2007).
[CrossRef]

Klein, M. W.

M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
[CrossRef]

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

König, M.

M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
[CrossRef]

Koschny, T.

J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic and electric excitations in split ring resonators,” Opt. Express 15, 17881–17890 (2007).
[CrossRef] [PubMed]

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
[CrossRef]

N. Katsarakis, T. Koschny, M. Kafesaki, E. N. Economou, and C. M. Soukoulis, “Electric coupling to the magnetic resonance of split ring resonators,” Appl. Phys. Lett. 84, 2943–2945 (2004).
[CrossRef]

S. Linden, C. Enkrich, M. Wegener, J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic response of metamaterials at 100 THz,” Science 306, 1351–1353 (2004).
[CrossRef] [PubMed]

Kuhl, J.

Kuipers, L.

M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, “Probing the Magnetic Field of Light at Optical Frequencies,” Science 23, 550–553 (2009).
[CrossRef]

Lam, P. K.

J. Janousek, K. Wagner, J. F. Morizur, N. Treps, P. K. Lam, C. C. Harb, and H. A. Bachor, “Optical entanglement of co-propagating modes,” Nat. Photonics 3, 399–402 (2009).
[CrossRef]

Lassen, M.

M. Lassen, G. Leuchs, and U. L. Andersen, “Continuous Variable Entanglement and Squeezing of Orbital Angular Momentum States,” Phys. Rev. Lett. 102, 163602 (2009).
[CrossRef] [PubMed]

Lederer, F.

Leinse, A.

M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, “Probing the Magnetic Field of Light at Optical Frequencies,” Science 23, 550–553 (2009).
[CrossRef]

Leuchs, G.

M. Lassen, G. Leuchs, and U. L. Andersen, “Continuous Variable Entanglement and Squeezing of Orbital Angular Momentum States,” Phys. Rev. Lett. 102, 163602 (2009).
[CrossRef] [PubMed]

J. Kindler, P. Banzer, S. Quabis, U. Peschel, and G. Leuchs, “Waveguide properties of single subwavelength holes demonstrated with radially and azimuthally polarized light,” Appl. Phys. B 89, 517–520 (2007).
[CrossRef]

R. Dorn, S. Quabis, and G. Leuchs, “Sharper Focus for a radially polarized light beam,” Phys. Rev. Lett. 91, 233901 (2003).
[CrossRef] [PubMed]

R. Dorn, S. Quabis, and G. Leuchs, “The focus of light – linear polarization breaks the rotational symmetry of the focal spot,” J. Mod. Opt. 50, 1917–1926 (2003).

S. Quabis, R. Dorn, M. Eberler, O. Glöckl, and G. Leuchs, “Focusing light to a tighter spot,” Opt. Commun. 179, 1 (2000).
[CrossRef]

Linden, S.

M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
[CrossRef]

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
[CrossRef]

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

S. Linden, C. Enkrich, M. Wegener, J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic response of metamaterials at 100 THz,” Science 306, 1351–1353 (2004).
[CrossRef] [PubMed]

Meier, M.

M. Meier, V. Romano, and T. Feurer, “Material processing with pulsed radially and azimuthally polarized laser radiation,” Appl. Phys., A Mater. Sci. Process. 86, 329–334 (2007).
[CrossRef]

Meixner, A. J.

T. Züchner, and A. V. Failla, A. Hartschuh, and A. J. Meixner, “A novel approach to detect and characterize the scattering patterns of single Au nanoparticles using confocal microscopy,” J. Microsc. 29, 337–343 (2008).
[CrossRef]

A. V. Failla, S. Jäger, T. Züchner, M. Steiner, and A. J. Meixner, “Topology measurements of metal nanoparticles with 1 nm accuracy by Confocal Interference Scattering Microscopy,” Opt. Express 15, 8532–8542 (2007).
[CrossRef] [PubMed]

Morizur, J. F.

J. Janousek, K. Wagner, J. F. Morizur, N. Treps, P. K. Lam, C. C. Harb, and H. A. Bachor, “Optical entanglement of co-propagating modes,” Nat. Photonics 3, 399–402 (2009).
[CrossRef]

Niegemann, J.

M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
[CrossRef]

Novotny, L.

J. R. Zurita-Sánchez, and L. Novotny, “Multipolar interband absorption in a semiconductor quantum dot. II. Magnetic dipole enhancement,” J. Opt. Soc. Am. B 19, 2722–2726 (2002).
[CrossRef]

L. Novotny, R. D. Grober, and K. Karrai, “Reflected image of a strongly focused spot,” Opt. Lett. 26, 789–791 (2001).
[CrossRef]

L. Novotny, M. R. Beversluis, K. S. Youngworth, and T. G. Brown, “Longitudinal Field Modes Probed by Single Molecules,” Phys. Rev. Lett. 23, 5251–5254 (2001).
[CrossRef]

B. Sick, B. Hecht, U. P. Wild, and L. Novotny, “Probing confined fields with single molecules and vice versa,” J. Microsc. 202, 365–373 (2000).
[CrossRef]

Peschel, U.

J. Kindler, P. Banzer, S. Quabis, U. Peschel, and G. Leuchs, “Waveguide properties of single subwavelength holes demonstrated with radially and azimuthally polarized light,” Appl. Phys. B 89, 517–520 (2007).
[CrossRef]

Prez-Willard, F.

C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
[CrossRef]

Quabis, S.

J. Kindler, P. Banzer, S. Quabis, U. Peschel, and G. Leuchs, “Waveguide properties of single subwavelength holes demonstrated with radially and azimuthally polarized light,” Appl. Phys. B 89, 517–520 (2007).
[CrossRef]

R. Dorn, S. Quabis, and G. Leuchs, “Sharper Focus for a radially polarized light beam,” Phys. Rev. Lett. 91, 233901 (2003).
[CrossRef] [PubMed]

R. Dorn, S. Quabis, and G. Leuchs, “The focus of light – linear polarization breaks the rotational symmetry of the focal spot,” J. Mod. Opt. 50, 1917–1926 (2003).

S. Quabis, R. Dorn, M. Eberler, O. Glöckl, and G. Leuchs, “Focusing light to a tighter spot,” Opt. Commun. 179, 1 (2000).
[CrossRef]

Rockstuhl, C.

Romano, V.

M. Meier, V. Romano, and T. Feurer, “Material processing with pulsed radially and azimuthally polarized laser radiation,” Appl. Phys., A Mater. Sci. Process. 86, 329–334 (2007).
[CrossRef]

Schadt, M.

Schmidt, F.

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

Schoenmaker, H.

M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, “Probing the Magnetic Field of Light at Optical Frequencies,” Science 23, 550–553 (2009).
[CrossRef]

Schönle, A.

N. Huse, A. Schönle, and S. W. Hell, “Z-polarized confocal microscopy,” J. Biomed. Opt. 6, 273–276 (2001).
[CrossRef] [PubMed]

Scully, M. O.

M. O. Scully, and M. S. Zubairy, “Simple laser accelerator: Optics and particle dynamics,” Phys. Rev. A 44, 2656–2663 (1991).
[CrossRef] [PubMed]

Sick, B.

B. Sick, B. Hecht, U. P. Wild, and L. Novotny, “Probing confined fields with single molecules and vice versa,” J. Microsc. 202, 365–373 (2000).
[CrossRef]

Soukoulis, C. M.

J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic and electric excitations in split ring resonators,” Opt. Express 15, 17881–17890 (2007).
[CrossRef] [PubMed]

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
[CrossRef]

S. Linden, C. Enkrich, M. Wegener, J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic response of metamaterials at 100 THz,” Science 306, 1351–1353 (2004).
[CrossRef] [PubMed]

N. Katsarakis, T. Koschny, M. Kafesaki, E. N. Economou, and C. M. Soukoulis, “Electric coupling to the magnetic resonance of split ring resonators,” Appl. Phys. Lett. 84, 2943–2945 (2004).
[CrossRef]

Stalder, M.

Steiner, M.

Treps, N.

J. Janousek, K. Wagner, J. F. Morizur, N. Treps, P. K. Lam, C. C. Harb, and H. A. Bachor, “Optical entanglement of co-propagating modes,” Nat. Photonics 3, 399–402 (2009).
[CrossRef]

van Oosten, D.

M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, “Probing the Magnetic Field of Light at Optical Frequencies,” Science 23, 550–553 (2009).
[CrossRef]

Wagner, K.

J. Janousek, K. Wagner, J. F. Morizur, N. Treps, P. K. Lam, C. C. Harb, and H. A. Bachor, “Optical entanglement of co-propagating modes,” Nat. Photonics 3, 399–402 (2009).
[CrossRef]

Wegener, M.

M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
[CrossRef]

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
[CrossRef]

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

S. Linden, C. Enkrich, M. Wegener, J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic response of metamaterials at 100 THz,” Science 306, 1351–1353 (2004).
[CrossRef] [PubMed]

Wild, U. P.

B. Sick, B. Hecht, U. P. Wild, and L. Novotny, “Probing confined fields with single molecules and vice versa,” J. Microsc. 202, 365–373 (2000).
[CrossRef]

Youngworth, K. S.

L. Novotny, M. R. Beversluis, K. S. Youngworth, and T. G. Brown, “Longitudinal Field Modes Probed by Single Molecules,” Phys. Rev. Lett. 23, 5251–5254 (2001).
[CrossRef]

K. S. Youngworth, and T. G. Brown, “Focusing of high numerical aperture cylindrical vector beams,” Opt. Express 7, 77–87 (2000).
[CrossRef] [PubMed]

Zentgraf, T.

Zhan, Q.

Zhou, J.

J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic and electric excitations in split ring resonators,” Opt. Express 15, 17881–17890 (2007).
[CrossRef] [PubMed]

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
[CrossRef]

S. Linden, C. Enkrich, M. Wegener, J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic response of metamaterials at 100 THz,” Science 306, 1351–1353 (2004).
[CrossRef] [PubMed]

Zhou, J. F.

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

Zschiedrich, L.

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

Zubairy, M. S.

M. O. Scully, and M. S. Zubairy, “Simple laser accelerator: Optics and particle dynamics,” Phys. Rev. A 44, 2656–2663 (1991).
[CrossRef] [PubMed]

Züchner, T.

T. Züchner, and A. V. Failla, A. Hartschuh, and A. J. Meixner, “A novel approach to detect and characterize the scattering patterns of single Au nanoparticles using confocal microscopy,” J. Microsc. 29, 337–343 (2008).
[CrossRef]

A. V. Failla, S. Jäger, T. Züchner, M. Steiner, and A. J. Meixner, “Topology measurements of metal nanoparticles with 1 nm accuracy by Confocal Interference Scattering Microscopy,” Opt. Express 15, 8532–8542 (2007).
[CrossRef] [PubMed]

Zurita-Sánchez, J. R.

Adv. Mater. (1)

C. Enkrich, F. Prez-Willard, D. Gerthsen, J. Zhou, T. Koschny, C. M. Soukoulis, M. Wegener, and S. Linden, “Focused-ion-beam nanofabrication of near-infrared magnetic metamaterials,” Adv. Mater. 17, 2547–2549 (2005).
[CrossRef]

Appl. Phys. B (1)

J. Kindler, P. Banzer, S. Quabis, U. Peschel, and G. Leuchs, “Waveguide properties of single subwavelength holes demonstrated with radially and azimuthally polarized light,” Appl. Phys. B 89, 517–520 (2007).
[CrossRef]

Appl. Phys. Lett. (1)

N. Katsarakis, T. Koschny, M. Kafesaki, E. N. Economou, and C. M. Soukoulis, “Electric coupling to the magnetic resonance of split ring resonators,” Appl. Phys. Lett. 84, 2943–2945 (2004).
[CrossRef]

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

M. Meier, V. Romano, and T. Feurer, “Material processing with pulsed radially and azimuthally polarized laser radiation,” Appl. Phys., A Mater. Sci. Process. 86, 329–334 (2007).
[CrossRef]

IEEE J. Sel. Top. Quantum Electron. (1)

S. Linden, C. Enkrich, G. Dolling, M. W. Klein, J. Zhou, T. Koschny, C. M. Soukoulis, S. Burger, F. Schmidt, and M. Wegener, “Photonic metamaterials: Magnetism at optical frequencies,” IEEE J. Sel. Top. Quantum Electron. 12, 1097–1105 (2006).
[CrossRef]

J. Biomed. Opt. (1)

N. Huse, A. Schönle, and S. W. Hell, “Z-polarized confocal microscopy,” J. Biomed. Opt. 6, 273–276 (2001).
[CrossRef] [PubMed]

J. Microsc. (2)

T. Züchner, and A. V. Failla, A. Hartschuh, and A. J. Meixner, “A novel approach to detect and characterize the scattering patterns of single Au nanoparticles using confocal microscopy,” J. Microsc. 29, 337–343 (2008).
[CrossRef]

B. Sick, B. Hecht, U. P. Wild, and L. Novotny, “Probing confined fields with single molecules and vice versa,” J. Microsc. 202, 365–373 (2000).
[CrossRef]

J. Mod. Opt. (1)

R. Dorn, S. Quabis, and G. Leuchs, “The focus of light – linear polarization breaks the rotational symmetry of the focal spot,” J. Mod. Opt. 50, 1917–1926 (2003).

J. Opt. Soc. Am. B (1)

Nat. Photonics (2)

J. Janousek, K. Wagner, J. F. Morizur, N. Treps, P. K. Lam, C. C. Harb, and H. A. Bachor, “Optical entanglement of co-propagating modes,” Nat. Photonics 3, 399–402 (2009).
[CrossRef]

M. Husnik, M. W. Klein, N. Feth, M. König, J. Niegemann, K. Busch, S. Linden, and M. Wegener, “Absolute extinction cross-section of individual magnetic split-ring resonators,” Nat. Photonics 2, 614–617 (2008).
[CrossRef]

Opt. Commun. (1)

S. Quabis, R. Dorn, M. Eberler, O. Glöckl, and G. Leuchs, “Focusing light to a tighter spot,” Opt. Commun. 179, 1 (2000).
[CrossRef]

Opt. Express (5)

Opt. Lett. (2)

Phys. Rev. A (1)

M. O. Scully, and M. S. Zubairy, “Simple laser accelerator: Optics and particle dynamics,” Phys. Rev. A 44, 2656–2663 (1991).
[CrossRef] [PubMed]

Phys. Rev. Lett. (4)

R. Dorn, S. Quabis, and G. Leuchs, “Sharper Focus for a radially polarized light beam,” Phys. Rev. Lett. 91, 233901 (2003).
[CrossRef] [PubMed]

L. Novotny, M. R. Beversluis, K. S. Youngworth, and T. G. Brown, “Longitudinal Field Modes Probed by Single Molecules,” Phys. Rev. Lett. 23, 5251–5254 (2001).
[CrossRef]

M. Lassen, G. Leuchs, and U. L. Andersen, “Continuous Variable Entanglement and Squeezing of Orbital Angular Momentum States,” Phys. Rev. Lett. 102, 163602 (2009).
[CrossRef] [PubMed]

C. Enkrich, M. Wegener, S. Linden, S. Burger, L. Zschiedrich, F. Schmidt, J. F. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic metamaterials at telecommunication and visible frequencies,” Phys. Rev. Lett. 95, 203901 (2005).
[CrossRef]

Science (2)

S. Linden, C. Enkrich, M. Wegener, J. Zhou, T. Koschny, and C. M. Soukoulis, “Magnetic response of metamaterials at 100 THz,” Science 306, 1351–1353 (2004).
[CrossRef] [PubMed]

M. Burresi, D. van Oosten, T. Kampfrath, H. Schoenmaker, R. Heideman, A. Leinse, and L. Kuipers, “Probing the Magnetic Field of Light at Optical Frequencies,” Science 23, 550–553 (2009).
[CrossRef]

Other (3)

P. R. Bevington, and K. D. Robinson, in Data Reduction and Error Analysis for the Physical Sciences, McGraw-Hill Inc., US, 2002, 3rd Ed.

Bi,norm = Bi/Ni with Ni = ? ?A(x0,y0)(?0/2 (|Ex|2 + |Ey|2))dxdy, Bi: maximum observed response derived from the line scan measurements, A(x0,y0): area of the SRR (metal area) centered at (x0,y0), and i = l, nl (l: SRR positioned in one of the main lobes; nl: SRR positioned on the nodal line).

We are still investigating the explanation for the observed diagonal asymmetry. We already have evidence, that the asymmetry is a interference between the light reflected by the substrate and the electric as well as the magnetic dipole emission. Provided the SRR is not positioned exactly on the optical axis or is a result of the non-perfect shape of the SRR.

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Figures (9)

Fig. 1.
Fig. 1.

(a) Experimentally recorded intensity distribution at a wavelength of 1.525 μm present at the entrance pupil of the focusing microscope objective in the setup. The white circle represents the diameter of the entrance pupil of the microscope objective (3.6 mm) in comparison to the intensity distribution (drawn to scale). The black dashed arrows show a snap-shot of the polarization. (b) Focusing scheme (x-z-plane) shown for the magnetic field vectors of a y-polarized TEM10-mode propagating in z-direction. A strong longitudinal magnetic field is formed on-axis in the focal plane, whereas the electric field is zero. Calculated energy density of the longitudinal magnetic field Hz in the focal plane. The small tilt of the field distribution is caused by the slight asymmetry of the incoming field. Cross-sections showing the calculated energy densities along (c) the nodal line (y-direction) and (d) perpendicular to the nodal line (x-direction) through the focal plane of a y-polarized TEM10-mode; μ02 Hz2 (solid green line), ε02 Ex2 (solid blue line in (e)), ε02 Ey2 (solid blue line in (f)) shown for a NA of 0.9 and a wavelength of 1.525 μm. The same arbitrary energy density unit is used in all graphs so that μ02 Hz2 and ε02 Ex2 as well as ε02 Ey2 can be compared. Note the different scales in (c) and (d). The generated transverse magnetic field components are not shown here.

Fig. 2.
Fig. 2.

(a) Experimental setup for investigating the response of a single nano-structure (SRR). LS: broadband light-source, LCSF: liquid-crystal spectral filter, LCPC: liquid-crystal polarization converter, LP: linear polarizer, M: mirrors, NPBS: non-polarizing beam splitter, MO: microscope objective (focusing MO) with an NA of 0.9; oil-immersion MO with an NA of 1.3 for collecting the transmitted light), PD: photodiode, CAM: camera, SRR: single split-ring resonator, GS: glass substrate. (b) Electron-micrograph of the investigated SRR design patterned into a 30 nm thick gold film (on a 170 μm thick glass substrate) using standard focused-ion-beam technique. SRR dimensions: h = 250 nm, w = 220 nm, b = 155 nm, a = 55 nm.

Fig. 3.
Fig. 3.

Experimental resonance spectra showing the transmitted (dashed black line; black circles) and reflected (solid red line; triangles) light of a single SRR centered in a linearly polarized and highly focused Gaussian beam. Two scenarios of the polarization orientation relative to the SRR arms are shown. (a) The electric field is perpendicular to the SRR arms. (b) The electric field is oriented parallel to the SRR arms. The pronounced resonance around 1.525 μm for a polarization perpendicular to the SRR arms is the lowest order or so-called magnetic resonance. The corresponding current distributions in the SRR for the resonances observed in a) and b) are depicted by the small insets. The experimental data points for the transmission and reflection spectra are normalized to the transmission through the glass substrate and the reflection at the air-glass interface, respectively.

Fig. 4.
Fig. 4.

Camera images of the reflected and collimated beam recorded with a bare camera sensor. The sample is illuminated with a strongly focused linearly polarized (y-direction) Gaussian beam. A crossed polarizer (x-components of the electric field can pass) is placed in front of the camera. The corresponding positions of the nano-structure relative to the beam are depicted on top of each camera image. (a) and (c): reflection at the glass substrate only; (b): SRR is placed in the beam; (d): rectangular nano-structure is placed in the beam. The cross-sections through the camera images (yellow solid lines) are shown next to the camera images. All camera images shown here were taken for a fixed wavelength of 1.525 μm. A clear fingerprint of a magnetic dipole radiation is observed in (b), if the SRR is placed in the beam (SRR arms perpendicular to the electric field).

Fig. 5.
Fig. 5.

Measurements of the intensities of the back-scattered and reflected light at a wavelength of 1.525 μm performed by scanning the focal plane of a y-polarized TEM10-mode. (a) Orientation of the single SRR relative to the electric field of the incoming beam (SRR arms perpendicular to the electric field). (b) Color-coded 2D scan image showing the reflected part of the focused beam measured as a function of the relative position of the center of the focused beam and the center of the SRR (recorded in the focal plane). The scanned field has an area of 5 μm times 5 μm. The step-size was set to 50 nm. (c) Line-scan through the maxima of the main lobes of the electric field in the focus (x-direction; perpendicular to the nodal line). 10 scans were averaged and normalized to the reflection at the glass substrate. The step-size was 50 nm. (d) Averaged and normalized scan result for scans along the nodal line. 66 line scans were averaged. The red curve represents the result of the iterative nonlinear least-squares fit routine. Bl and Bnl represent the maximum response achieved for the scan perpendicular to the nodal line (SRR in one of the main lobes of the electric field) and along the nodal line, respectively.

Fig. 6.
Fig. 6.

Same as Fig. 5 but for a different orientation of the single SRR relative to the electric field of the incoming beam (SRR arms parallel to the electric field; see (a)). The inset in (d) shows a sketch of two coupling scenarios achieved for a scan along the nodal line. The additional overlap with the crossed electric field components on the nodal line (dark blue areas) leads to a shift (Δy) of the position of the observed maximum.

Fig. 7.
Fig. 7.

Same as Fig. 5 but for a different wavelength of 1400 nm. The SRR is oriented as depicted in (a).

Fig. 8.
Fig. 8.

Same as Fig. 7 but for a different orientation of the single SRR relative to the electric field of the incoming beam (SRR arms parallel to the electric field; see (a)). The wavelength was set to 1400 nm.

Fig. 9.
Fig. 9.

Comparison between the resonance spectra (dashed black line; reflection only) of the tested SRR and the scan results achieved for coupling with different field distributions present in the focus of a y-polarized TEM10-mode (solid red stars: SRR sitting in one of the main lobes; solid green hexagon: SRR sitting on the nodal line with arms pointing upwards). The presented data points resulting from the scan measurements are renormalized to the overlap with the electric field energy density in the focus for different wavelengths. For each of the three geometries shown in the insets the reflection was measured at two different wavelengths (green and red data points). For each geometry the data point measured at 1.525 μm and normalized to the incident electric field energy was scaled to fit to the resonance spectrum (dashed line). The data point at 1.4 μm was plotted using the same scale factor. The resonance spectra were recorded with a linearly polarized Gaussian beam. (a) Spectra taken for linear electric field aligned perpendicular to the SRR arms. (b) For the electric field parallel to the SRR arms.

Equations (1)

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f(x)=A+B×exp(2(xx0)2ω2).

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