Doctoral Dissertations

Date of Award

5-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

Hanno Weitering

Committee Members

Gerd Duscher, Ramki Kalyanaraman, Marianne Breinig, Jian Liu, Tatiana Allen

Abstract

The linear optical, and nonlinear optical and magneto-optical properties of plasmonic nanostructures offer important guidelines for designing nanoscale all-optical and quantum optical devices with ultra-fast response time. This dissertation work presents the study of those properties in Ag, FeAg and CoAg metallic nanostructures. While UV-Vis-NIR spectroscopy and modified Z-scan techniques were used to study the linear and nonlinear properties, electron energy-loss spectroscopy performed in scanning transmission electron microscopy mode was employed to investigate and evaluate those properties. This work also present the synthesis techniques of those nanostructures. The Ag and Co-Ag nanoparticles were synthesized by pulsed laser melting of thin fims while Fe-Ag bimetallic arrays were fabricated by nanosphere lithography techniques. Near-spherical Ag nanoparticles were synthesized by Ultra Violet (UV) laser dewetting of Ag thin films under a glycerol fluid environment. Under a single 9 nanosecond laser pulse irradiation of the particles in air, the particles were changed into a near-hemispherical shape. The resulting changes in particle contact area and volume fraction in the dielectric media resulted in substantial shift in the wavelength and intensity of the dipolar and quadrupolar LSPR modes to the violet side of the visible spectrum. Fe-Ag bimetallic hexagonally ordered nanopyramidal arrays showed the giant negative nonlinear refraction and nonlinear Faraday rotation at telecommunication wavelength of 1550 nm. Further, the nonlinear response was dependent on the degree of overlap of the Fe nanopyramid on the Ag nanopyramid which influenced the strength of plasmon induced dipoles on the Ag nanopyramid. The analysis of optical spectra and electron energy loss spectra of Co-Ag nanoparticles led to detection of localized surface plasmons at the interface of two metals ever observed from bimetallic nanoparticles. These investigations and findings generally advance the science of plasmonic nanostructures towards optical, magneto-optical and quantum-optical based applications.

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