Séminaire

Mardi 1^er Octobre 2019 à 11h00.

Enhancing and Steering Harmonic Generation in Plasmonic and Dielectric Nanoantennas

''L'équipe Optique non linéaire et interfaces invite Michele Celebrano de Politecnico Milano.
Abstract. Nanoscale optical integration is nowadays a strategic technological challenge and the ability of generating and manipulating nonlinear optical processes in sub-wavelength volumes is a key-enabling asset for the realization of efficient sensing probes for sensing and photonic sources for the next-generation communication technologies. Yet, to date, confining nonlinear processes beyond the diffraction limit remains a challenging task because phase-matching conditions, which ensure efficient energy transfer from the fundamental to the nonlinear wave in the bulk, cannot be exploited at the nanoscale. Significant efforts have been recently devoted to the investigation of nonlinear optical processes in plasmonic nanoantennas [1,2]. The strong local field enhancements they yield make them, to date, extremely promising candidates to overcome the lack of phase-matching at the nanoscale. In this framework, we have devised an approach to enhance the second harmonic generation (SHG) in non-centrosymmetric plasmonic nanoantennas [3]. We recently applied this concept to an extended array of non-centrosymmetric nanoantennas for sensing applications [4]. I will also show that, thanks to the high SHG efficiency associated with the broken symmetry in these nanoantennas, it is possible to retrieve the evidence of a cascaded second-order process in higher-order nonlinear processes, like Third Harmonic Generation (THG) [5]. Recently, dielectric nanoantennas re-established as an alternative solution to plasmonic ones to enhance nonlinear emission at the nanoscale, thanks to their sharp magnetic and electric Mie resonances along with the low ohmic losses visible/near-infrared region of the spectrum. I will present our most recent studies on AlGaAs nanopillars, demonstrating an extremely high SHG efficiency associated with the bulk second-order susceptibility of the material [6,7]. In this frame, I will also disclose a few key strategies we have recently undertook to manipulate the SHG at the nanoscale even on ultrafast time scales. Finally, I will show how to effectively engineer Sum Frequency Generation (SFG) via the Mie resonances in these nanoantennas. These results set the basis for all optical logic operation at room temperature on the nanoscale.

1. M. Kauranen, A. V. Zayats. Nature Photonics 6, 737–748, 2012.
2. J. Butèt et al. ACS Nano 9, 10545–10562, 2015.
3. M. Celebrano et al. Nature Nanotechnology 10, 412–417, 2015.
4. L. Ghirardini et al. J. Phys. Chem. C 122, 11475-11481, 2018.
5. M. Celebrano et al. Nanoletters 2019, Article ASAP DOI:10.1021/acs.nanolett.9b02427
6. V. Gili et al. Opt. Exp. 24, 15965, 2016.
7. L. Ghirardini et al. Opt. Lett. 42, 559-562, 2017.
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