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

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

Ko, Kaspar D. ; Toussaint ; Kimani C.

关键词: 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;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/24336/Ko_Kaspar.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

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.