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Title:Nonlinear optical emission and near-field enhancement effects in arrays of gold bowtie nano-antennas
Author(s):Ko, Kaspar D.
Advisor(s):Toussaint, Kimani C.
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
photonics near-field enhancement
field enhancement
field confinement
laser-induced damage
plasmonically enhanced optical trap
optical tweezers
second-harmonic generation
gold nanostructure
two-photon photoluminescence
supercontinuum generation
bowtie nano-antenna
periodic arrays
array effect
resonant enhancement
trapping regime
coupled-plasmon resonant-nanoparticle pair geometry
Abstract:This thesis investigates the effects of the large near-field intensity enhancements from periodic arrays of gold bowtie nano-antennas (BNAs) after illumination by laser light. Specifically, we focus on laser-induced damage, nonlinear optical emission, and a proof-of-concept for utilizing arrays of gold BNAs to enhance the forces in an optical trapping system. From FDTD simulations, the optical response of a single BNA is demonstrated to increase the local intensity by a factor of 1000 in the feed-gap region by using a periodic array. Because of the high near-field intensities, inherently weak nonlinear optical processes become enhanced, and we take advantage of these favorable conditions to investigate the dependence of second-harmonic generation and two-photon photoluminescence emission intensities with respect to the array periodicity and the incident polarization. A detrimental side-effect of the efficient radiative coupling to the incident light and high near-field intensities is laser-induced damage, which may alter the morphology of the BNA structures at sufficiently high laser fluences. A damage threshold is systematically determined in terms of irradiation time and average incident power after implementation of damage reduction measures including laser pulse-width optimization, a stochastic beam-scanning pattern, and the use of a chromium adhesion layer. Finally, the increased optical forces in a trapping system resulting from the field enhancement of arrays of BNAs is demonstrated. In addition, based on the exclusive behaviors of these types of systems, a new method of characterizing plasmonically enhanced optical traps is proposed.
Issue Date:2011-05-25
Rights Information:Copyright 2011 Kaspar D. Ko
Date Available in IDEALS:2011-05-25
Date Deposited:2011-05

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