Nonlinear optical emission and near-field enhancement effects in arrays of gold bowtie nano-antennas

Ko, Kaspar D.

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https://hdl.handle.net/2142/24336 Copy

Description

Title

Nonlinear optical emission and near-field enhancement effects in arrays of gold bowtie nano-antennas

Author(s)

Ko, Kaspar D.

Issue Date

2011-05-25T14:53:34Z

Director of Research (if dissertation) or Advisor (if thesis)

Toussaint, Kimani C.

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• optics
• photonics near-field enhancement
• field enhancement
• field confinement
• nano-antenna
• nanophotonics
• 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
• trampolining
• trapping regime
• nano-dimers
• 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.

Graduation Semester

2011-05

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http://hdl.handle.net/2142/24336

Copyright and License Information

Copyright 2011 Kaspar D. Ko

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