Nordlander , Peter2022-09-232022-122022-08-22December 2Naidu, Gopal Narmada. "Theoretical Characterization of the Optical Properties of Plasmonic Nanostructures." (2022) Master’s Thesis, Rice University. <a href="https://hdl.handle.net/1911/113292">https://hdl.handle.net/1911/113292</a>.https://hdl.handle.net/1911/113292Since Faraday’s investigation of colloidal gold in the mid-1800s, the optical properties of metal nanoparticles have long been of interest albeit their nanoscale dimensions and presence of surface plasmon resonances. More, recently, new lithographic techniques as well as improvements to classical wet chemistry methods have made it possible to synthesize metal nanoparticles with a wide range of sizes, shapes and dielectric environments, enabling more intriguing optical properties such as circular dichroism response by chiral structures, hot spots by close gap between nanoparticles, geometry-dependent resonance wavelengths, and Fano resonances. Optical investigative methods in comparison to electrical or mechanical methods take advantage of observing these characteristics of nanomaterials without significantly modifying or permanently damaging them due to their noncontact and noninvasive probing nature. In this thesis, we work together with our experimental collaborators who synthesize these nanostructures and utilize state-of-the-art spectroscopic techniques to measure a range of optical properties for various practical applications. We develop theoretical methods and models using advanced numerical simulations and modelling to elucidate and explain the mechanisms behind these observed unique optical features. In the first part of the thesis, we use Finite Difference Time Domain (FDTD) method to characterize the optical properties of selectively faceted aluminum nanocrystals synthesized using a novel dual-catalyst strategy under single particle dark-field spectroscopic excitation. We show clear agreement between the experimental and simulated spectra and further use charge distributions along with multipole analysis to understand the mechanism behind the observed scattering spectra. In the second chapter, using the Finite Element Method (FEM) we investigate the differential scattering of electron-beam lithographically fabricated rotationally symmetric chiral plasmonic pinwheels when they are asymmetrically irradiated with linearly polarized light. We demonstrate orientation-independent linear differential scattering that arises due to the broken mirror and rotational symmetry of our overall experiment geometry. On the whole, this thesis demonstrates the adept use of theoretical methods and models to provide intuitive insights into complex nanostructure properties and experimental conditions.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.Plasmonicsoptical characterizationThesis2022-09-23