Doubling the Efficiency of Third Harmonic Generation by Positioning ITO Nanocrystals into the Hot-Spot of Plasmonic Gap-Antennas

• Published in: Nano letters Vol. 14; no. 5; pp. 2867 - 2872
• Main Authors: Metzger, Bernd, Hentschel, Mario, Schumacher, Thorsten, Lippitz, Markus, Ye, Xingchen, Murray, Christopher B, Knabe, Bastian, Buse, Karsten, Giessen, Harald
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 14.05.2014
• Subjects: Antennas; Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Gold; Harmonic generations; Harmonics; Indium tin oxide; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials science; Nanocrystalline materials; Nanocrystals; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics; Plasmonics; Surface and interface electron states; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Nano-optics; third harmonic generation; nonlinear optics; plasmonics; spectroscopy; Gold; Digital simulation; Harmonic generation; Nanostructures; Indium oxide; Finite element method; Tin oxide; Optical properties; Plasmons; Resonance; Arrays; Nanostructured materials; Antennas; Nanocrystal
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl500913t

We incorporate dielectric indium tin oxide nanocrystals into the hot-spot of gold nanogap-antennas and perform third harmonic spectroscopy on these hybrid nanostructure arrays. The combined system shows a 2-fold increase of the radiated third harmonic intensity when compared to bare gold antennas. In order to identify the origin of the enhanced nonlinear response we perform finite element simulations of the nanostructures, which are in excellent agreement with our measurements. We find that the third harmonic signal enhancement is mainly related to changes in the linear optical properties of the plasmonic antenna resonances when the ITO nanocrystals are incorporated. Furthermore, the dominant source of the third harmonic is found to be located in the gold volume of the plasmonic antennas.