"Magnetoplasmonic nanoantennas: theory and applications"

Who: Nicolo Maccaferri, Nanomagnetism Group

Place: nanoGUNE seminar room, Tolosa Hiribidea 76, Donostia - San Sebastian

Date: Monday, 29 June 2015, 11:00

The rapidly developing field of magnetoplasmonics merges the concepts from plasmonics and magnetism to realize novel and unexpected phenomena for the manipulation of light at the nanoscale.
Ferromagnetic nanoantennas support localized surface plasmons and exhibit sizeable magneto-optical activity under external magnetic fields [1-3]. Here we explore the influence of the phase of localized surface plasmon resonances on the magneto-optical activity of ferromagnetic nanoantennas. 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 and active role on the magneto-optical properties by controlling the relative amplitude and phase lag between the two oscillators [3]. The theoretical predictions are fully confirmed by magneto-optical Kerr effect and optical extinction measurements in nanostructures of different size and shape.
We also present an overview of potential technological applications of magnetoplasmonic nanoantennas, opening new perspectives towards a variety of emerging technologies such as ultrasensitive molecular sensing [4], non-reciprocal metasurfaces for the control of the light polarization states at the nanoscale [5], and out-performing plasmon rulers [6].
Based on our previous theoretical findings, we first show novel ways to exploit such nanoantennas for the active manipulation of the light polarization states. We introduce design rules for highly tunable active magnetoplasmonic elements in which we can tailor at will the amplitude and sign of the Kerr response over a broad spectral range [4].
Then we demonstrate how magnetoplasmonic nanoantennas can be exploited as ultrasensitive sensors for biotechnological applications [5]. Systems allowing label-free molecular detection are expected to have enormous impact on biochemistry and biomedicine, and are therefore subject to intense investigation. We propose an innovative and alternative route based on magnetoplasmonic nanoantennas, which enables radically improved sensitivity, clearly outperforming recently reported plasmon based sensors. Most remarkably, we achieved a local surface sensitivity of two orders of magnitude higher than the best values reported for nanoplasmonic sensors. Such sensitivity corresponds to a mass of ~0.8 atto g/nanoantenna of polyamide-6.6 (n=1.51), which is representative for a large variety of polymers, peptides and proteins.
Finally, we focused on the emerging concept of plasmon rulers, in which strong near-field coupling of plasmon antenna elements is employed to obtain structural information on the nanoscale. We demonstrate how magnetoplasmonic rulers based on ferromagnetic dimers allow for the measurements of small and large nanoscale distances alike with two orders of magnitude higher precision than current state-of-the-art plasmon rulers [6].
[1] J. Chen et al. Small 7, 2341 (2011).
[2] V. Bonanni et al. Nano Lett. 11, 5333 (2011).
[3] N. Maccaferri et al. Phys. Rev. Lett. 111, 167401 (2013).
[4] K. Lodewijks et al., Nano Lett. 14, 7207 (2014).
[5] N. Maccaferri et al., Nat. Commun. 6, 6150 (2015).
[6] I. Zubritzskaya et al., Nano Lett., 15, 3204 (2015).

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