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Plasmonic excitations are usually attributed to the free electron response at visible frequencies in the classic plasmonic metals Au and Ag. However, the vast majority of metals exhibit spectrally localized interband transitions or broad interband transition backgrounds in the energy range of interest for nanoplasmonics. Nevertheless, the interaction of interband transitions with localized plasmons in optical nanoantennas has hitherto received relatively little attention, probably because interband transitions are regarded as highly unwanted due to their strong damping effect on the localized plasmons. However, with an increasing number of metals (beyond Au and Ag) being considered for nanoplasmonic applications such as hydrogen sensing (Pd), UV-SERS (Al), or magnetoplasmonics (Ni, Fe, Co), a deeper conceptual understanding of the interactions between a localized plasmon mode and an interband transition is very important. Here, as a generic example, we examine the interaction of a localized (in energy spa...

We introduce a new perspective on magnetoplasmonics in nickel nanoferromagnets by exploiting the phase tunability of the optical polarizability due to localized surface plasmons and simultaneous magneto-optical activity. We demonstrate how the concerted action of nanoplasmonics and magnetization can manipulate the sign of rotation of the reflected light’s polarization (i.e., to produce Kerr rotation reversal) in ferromagnetic nanomaterials and, further, how this effect can be dynamically controlled and employed to devise conceptually new schemes for biochemosensing. © 2011 American Chemical Society., A.D. and Z.P. acknowledge support from the Swedish Research Council and Swedish Foundation for Strategic Research (Framework program Functional Electromagnetic Metamaterials, project RMA08). J.Å. acknowledges support from the Swedish Research Council, the Swedish Foundation for Strategic Research (Future Research Leader Programme), and the G€oran Gustafsson Foundation. J.Å. is a Royal Swedish Academy of Sciences Research Fellow supported by a grant from the Knut and Alice Wallenberg Foundation. V.B. acknowledges the G€oran Gustafsson Foundation and the Blanceflor Boncompagni-Ludovisi Foundation. P.V. acknowledges funding from the Basque Government through the ETORGAI Program, Project No. ER- 2010/00032 and Program No. PI2009-17, the Spanish Ministry of Science and Education under Projects No. CSD2006-53 and No. MAT2009-07980. J.N. acknowledges funding for the Generalitat de Catalunya and the Spanish Ministry of Science and Education through No. 2009-SGR-1292 and No. MAT2010-20616-C02 projects.

7 páginas, 6 figuras.-- El pdf del artículo es la versión post-print.-- et al., The fundamental optical properties of pure nickel nanostructures are studied by far-field extinction spectroscopy and optical near-field microscopy, providing direct experimental evidence of the existence of particle plasmon resonances predicted by theory. Experimental and calculated near-field maps allow for unambiguous identification of dipolar plasmon modes. By comparing calculated near-field and far-field spectra, dramatic shifts are found between the near-field and far-field plasmon resonances, which are much stronger than in gold nanoantennas. Based on a simple damped harmonic oscillator model to describe plasmonic resonances, it is possible to explain these shifts as due to plasmon damping., Supported by the European FP7 project ‘Nanoantenna’ (FP7-HEALTH-F5-2009-241818-NANOANTENNA) and the National Project MAT2009 –08398 from the Spanish Ministerio de Ciencia e Innovacion. J.A. acknowledges fi nancial help by the Department of Industry of the Basque Government through the ETORTEK program NANOPHOT. P.V. acknowledges funding from the Basque Government under Programs No. PI2009–17 as well as the Spanish Ministry of Science and Education under Project No. MAT2009–07980. Z. P. acknowledges support from Swedish Foundation for Strategic Research through RMA08–0109 “Functional Electromagnetic Metamaterials” program. J. N. acknowledges funding from the Generalitat de Catalunya and the Spanish Ministry of Science and Education through No. 2009-SGR-1292 and No. MAT2010–20616-C02 projects. A.D. acknowledges support from the Swedish Research Council.

Nature Communications 6: Article number: 6150 (2015). Published 2 February 2015; Updated 18 June 2015. This Article contains typographical errors in the equations of the last sentence of the first paragraph of the Results section. This sentence should read ‘In the present case, the spin–orbit transversally induced dipole is given by (considering the circular shape of our nanoantennas, αyy=αxx, that is, the two LPRs resonate at the same wavelength, and the expression above can be simplified to’

Systems allowing label-free molecular detection are expected to have enormous impact on biochemical sciences. Research focuses on materials and technologies based on exploiting localized surface plasmon resonances in metallic nanostructures. The reason for this focused attention is their suitability for single-molecule sensing, arising from intrinsically nanoscopic sensing volume and the high sensitivity to the local environment. Here we propose an alternative route, which enables radically improved sensitivity compared with recently reported plasmon-based sensors. Such high sensitivity is achieved by exploiting the control of the phase of light in magnetoplasmonic nanoantennas. We demonstrate a manifold improvement of refractometric sensing figure-of-merit. Most remarkably, we show a raw surface sensitivity (that is, without applying fitting procedures) of two orders of magnitude higher than the current values reported for nanoplasmonic sensors. Such sensitivity corresponds to a mass of ~0.8 ag per nanoantenna of polyamide-6.6 (n=1.51), which is representative for a large variety of polymers, peptides and proteins.

An approach to compute the polarizability tensor of magnetic nanoparticles having general ellipsoidal shape is presented. We find a surprisingly excellent quantitative agreement between calculated and experimental magneto-optical spectra measured in the polar Kerr configuration from nickel nanodisks of large size (exceeding 100 nm) with circular and elliptical shape. In spite of its approximations and simplicity, the formalism presented here captures the essential physics of the interplay between magneto-optical activity and the plasmonic resonance of the individual particle. The results highlight the key role of the dynamic depolarization effects to account for the magneto-optical properties of plasmonic nanostructures. © 2013 Optical Society of America., N. M., J. B. G-D, A. B. and P. V. acknowledge support from the Basque Government under the Etortek Program IE11-304 and the project PI2012-47 and the Spanish Ministry of Education under the Project No. MAT2012-36844. S. B. acknowledges the Knut and Alice Wallenberg Foundation. M. K. and S. v. D. acknowledge support from the National Doctoral Programme in Nanoscience and the Academy of Finland (grant no. 263510). V. B. acknowledges the Göran-Gustafsson Foundation and the Blanceflor Boncompagni-Ludovisi Foundation. J. N. acknowledges the Generalitat de Catalunya under the project 2009-SGR-1292 and the Spanish Ministerio de Economía y Competitividad under the project MAT2010-20616-C02. A. D. and Z. P. acknowledge support from the Swedish Research Council and Swedish Foundation for Strategic Research (Framework program Functional Electromagnetic Metamaterials, project RMA08).

et al., We explore the influence of the phase of localized plasmon resonances on the magneto-optical activity of nanoferromagnets. We demonstrate that these systems can be described as two orthogonal damped oscillators coupled by the spin-orbit interaction. We prove that only the spin-orbit induced transverse plasmon plays an active role on the magneto-optical properties by controlling the relative amplitude and phase lag between the two oscillators. Our theoretical predictions are fully confirmed by magneto-optical Kerr effect and optical extinction measurements in nanostructures of different size and shape. © 2013 American Physical Society., We thank for financial support the Basque Government (Program No. PI2012-47), the Catalan Government (Project No. 2009-SGR-1292), and the Spanish Ministry of Economy and Competitiveness (Projects No. MAT2012-36844 and No. MAT2010-20616-C02). S. B. and J.Å. acknowledge financial support from the Knut and Alice Wallenberg Foundation. Z. P., A. D., and J.Å. acknowledge the Swedish Research Council (VR) and the Swedish Foundation for Strategic Research, SSF (Z. P. and A. D.: Framework program Functional Electromagnetic Metamaterials, Project No. RMA08; J.Å.: Successful Research Leader Program). M. K., Q. H. Q, and S. v. D. acknowledge support from the National Doctoral Programme in Nanoscience and the Academy of Finland (Grant No. 263510).