title: Silencing and enhancement of second-harmonic generation in optical gap antennas.
abstract: Amplifying local electromagnetic fields by engineering optical interactions between individual constituents of an optical antenna is considered fundamental for efficient nonlinear wavelength conversion in nanometer-scale devices. In contrast to this general statement we show that high field enhancement does not necessarily lead to an optimized nonlinear activity. In particular, we demonstrate that second-harmonic responses generated at strongly interacting optical gap antennas can be significantly suppressed. Numerical simulations are confirming silencing of second-harmonic in these coupled systems despite the existence of local field amplification. We then propose a simple approach to restore and amplify the second-harmonic signal by changing the manner in which electrically-connected optical antennas are interacting in the charge-transfer plasmon regime. Our observations provide critical design rules for realizing optimal structures that are essential for a broad variety of nonlinear surface-enhanced characterizations and for realizing the next generation of electrically-driven optical antennas.
authors.affiliation: Laboratoire Interdisciplinaire Carnot de Bourgogne CNRS-UMR 6303, Université de Bourgogne, Dijon, France.
authors.forename: Johann
authors.initials: J
authors.lastname: Berthelot
authors.forename: Guillaume
authors.initials: G
authors.lastname: Bachelier
authors.forename: Mingxia
authors.initials: M
authors.lastname: Song
authors.forename: Padmnabh
authors.initials: P
authors.lastname: Rai
authors.forename: Gérard
authors.initials: G
authors.lastname: Colas des Francs
authors.forename: Alain
authors.initials: A
authors.lastname: Dereux
authors.forename: Alexandre
authors.initials: A
authors.lastname: Bouhelier
mesh_terms: D003198:Computer Simulation; D004574:Electromagnetic Fields; D060733:Electromagnetic Radiation; D004583:Electrons; D004867:Equipment Design; D006046:Gold / Q000737:chemistry; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008962:Models, Theoretical; D036103:Nanotechnology / Q000379:methods*; D055095:Optics and Photonics / Q000379:methods*; D012542:Scattering, Radiation; D013499:Surface Properties
chemical_list: D006046:Gold