Author:

Keywords:

Plasmonics, nano-optics, Fano resonance

Abstract:

Localized surface plasmons are collective electron oscillations in metallic nanostructures at optical frequencies. These nanostructures can therefore be considered as optical nanoantennas or classical harmonic oscillators at the nanoscale. Applications of surface plasmon resonances are widespread, nurtured by nanotechnology, and approaching a level of maturity that gives them a prominent position to contribute to some of today’s most important challenges: energy harvesting, cancer treatment, disease diagnostics, DNA sequencing, and optical computing. A detailed control over the basic resonance characteristics - the resonance frequency, line width and line shape - forms the foundation for a successful development of such plasmonics-based technologies. We present fundamental ways to control, through nanostructuring, the line width and line shape of localized surface plasmon resonances (LSPR) in individual coherent plasmonic nanocavities. Our approach towards plasmonic line shaping focuses on the control of radiative losses by coupling different plasmonic resonators sustaining dipole and multipole resonances. This gives rise to subradiant and superradiant modes [1]. Moreover, the coherent coupling of these subradiant and superradiant plasmon resonances can result in Fano interference with asymmetric line shapes [2]. Our results for relatively simple nanostructures form a fundamental basis for the design and understanding of new, more advanced plasmonic nanosystems [3]. As an example, the immediate relevance of subradiant and Fano resonances for refractive index sensing applications (e.g. biosensing) is demonstrated [4]. [1] Y. Sonnefraud, N. Verellen, H. Sobhani, G.A.E. Vandenbosch, V. V. Moshchalkov, P. Van Dorpe, P. Nordlander, and S. A. Maier, ACS Nano 4(3), 1664–1670, 2010. [2] N. Verellen, Y. Sonnefraud, H. Sobhani, F. Hao, V. V. Moshchalkov, P. Van Dorpe, P. Nordlander, and S. A. Maier, Nano Letters, 9(4), 1663–1667, 2009. [3] N. Verellen, P. Van Dorpe, D. Vercruysse, G. A. E. Vandenbosch, and V. V. Moshchalkov, Optics Express 19(12), 11034–11051, 2011. [4] N. Verellen, P. Van Dorpe, C. Huang, K. Lodewijks, G. A. E. Vandenbosch, L. Lagae, and V. V. Moshchalkov, Nano Letters 11(2), 391–397, 2011.