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Accueil > Séminaires > Archive des séminaires d’Utinam > 2018

Thierry Grosjean

Plasmonics and nano-antennas, some achievements realized at FEMTO-ST Institute

mercredi 10 octobre 2018, 14h

salle de conférences de l’observatoire

Thierry GROSJEAN

Institut FEMTO-ST
Mots-clés :
Optiques, rayons X, nano-optique, nano-antennes, antennes optiques, plasmonique, interaction lumière-matière, Microscopie en champ proche, ondes évanescentes, plasmons de surface, interaction spin-orbite optique

Résumé :

The wavelength is a central parameter in optics. Besides its direct relationship with colors and photon energy, it defines the limit between two different optical regimes. Optics at scales larger than the wave-length is directly perceived with our eyes. It involves free space propagating light (under the form of plane waves, spherical waves, etc.) and is nowadays involved in an extremely broad panel of scientific, medical and industrial researches and applications ranging from astronomy to microscopy. Optics at sub-wavelength scale, called “nano-optics”, involves another type of optical waves, called “evanescent waves”, which are bound to object surfaces and cannot leave them to propagate in free space.

Research in nano-optics is aimed at understanding the optical phenomena at the subwavelength scale. It essentially relies on the ability to control light-matter interaction on the nanometer scale with specifically designed nanostructures. The improvement of nanoscale fabrication technologies in the past decades has for instance allowed the investigation of giant optical phenomena on metallic nanoparticles, leading to the concept of nano-antennas.

Nano-antennas are the result of the extension to optics of the well-known concept of electromagnetic antennas used at lower frequencies (radio and microwave frequencies). As their low frequency counterparts, nano-antennas are aimed at efficiently interconnecting free-space propagating electromagnetic waves (here, light) with highly localized sources and fields. They provide interfaces to make the nano-world efficiently communicate and interact with the macroscale. The ability of nano-antennas to concentrate light on the nanometer scale is for example widely exploited to locally enhance inherently weak optical effects and to control the emission from fundamental light sources, such as fluorescent molecules, quantum dots, fluorescent particles, etc. Remarkably, nano-antenna’s optical properties can be finely tuned by slightly changing the shape and size of their constitutive metallic parts. Such a property enables the accurate engineering of light-matter interaction and its ultimate control well beyond the diffraction limit, thus impacting vast scientific and potentially economic domains.

I will present some works conducted at FEMTO-ST dealing with the development and application of nano-antennas. I will show how nano-antennas can contribute to the scanning near-field optical microscopy (SNOM), and also what SNOM techniques have brought to the investigation of light-matter interaction with nano-antennas. Finally, I will show one of the first ways to tune sub-diffraction plasmonics with the optical polarization, thanks to the so-called “spin-orbit-interaction” of light (SOI). We applied the SOI to tune the excitation of two nano-antennas connected at the two ends of a nanoscale plasmonic waveguide, by reaching spin-controlled unidirectional propagation of the guided optical waves that feed the nano-antennas. I will also introduce the concept of magnetic spin-orbit interaction of light that we recently demonstrated with Bloch surface waves on a 1D photonic crystal.

Version imprimable (PDF) :

PDF - 10.4 ko