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Download fileThird-Harmonic Generation Enhancement by Film-Coupled Plasmonic Stripe Resonators
journal contribution
posted on 19.11.2014, 00:00 authored by J. Britt Lassiter, Xiaoshu Chen, Xiaojun Liu, Cristian Ciracì, Thang B. Hoang, Stéphane Larouche, Sang-Hyun Oh, Maiken H. Mikkelsen, David R. SmithBecause of their
ability to strongly localize and enhance optical
fields, plasmonic nanostructures have the potential to dramatically
amplify the inherent nonlinear response of materials. We illustrate
the impact of this plasmonic interaction by investigating the third-harmonic
generation (THG) from a system of film-coupled nanostripes operating
at 1500 nm. Both the film and the stripes are gold, separated by a
nanoscale layer of aluminum oxide (Al2O3) grown
using atomic layer deposition. This nanoscale junction, with an ultrasmooth
interface, forms a waveguide cavity resonator with a large and controllable
electric field enhancement, whose plasmon resonance can be tuned independently
by changing the stripe width. We study experimentally the dependence
of THG on the field enhancement by varying the gap size between the
stripe and the metal film while simultaneously maintaining a fixed
plasmon resonance. The experiments are supported with numerical simulations
in which nonlinear contributions of the dielectric spacer layer and
the metal are considered. Enhancements of the THG of nearly 5 orders
of magnitude with respect to a bare metal film are measured experimentally
for the smallest gap sizes, with a trend similar to that found in
the numerical simulations.