Theoretical Studies on Localized Surface Plasmon Resonances of Nanoparticle Arrays—Standing-Wave Modes Optical Phase Characteristics and Rayleigh Anomalies

Abstract

This thesis presents theoretical studies on the optical characteristics of localized surface plasmon resonances (LSPRs) in spectra of periodic nanoparticle arrays Three subjects have been discussed: the excitations of standing-wave modes in split-ring resonators (SRRs) the optical phase characteristics of nanodot arrays and the impacts of Rayleigh anomalies on LSPR spectra We investigate the excitations of standing-wave modes of SRRs with different incident angles and polarizations Two changes at oblique incidence with respect to normal incidence are investigated—the excitations of dark modes with linear polarizations and the deviation of spectra of right- and left-handed circular polarizations We find that the parallelism between the incident electric field and the induced plasmon current is the key factor affecting the excitation We propose the use of a P-factor to characterize the ability of incident fields to excite standing-wave modes We analytically model the intensity and the phase spectra of silver nanodots with temporal-coupled mode theory (TCMT) The focus is on phase characteristics that are a π jump for reflection and a zigzag transition for transmission We derive the equation of phase slope at the zigzag transition of transmission The equation shows that the Ohmic absorption decreases the phase slope We further investigate plasmonic phase retardation in anisotropic nanodot arrays We discovered that the bandwidth of phase retardation could be much narrower than the LSPR bandwidth if the long and the short side lengths of the nanodots are very close We propose the application of plasmonic phase retardation in refractive index sensing In this sensing algorithm the sensor figure-of-merit is greatly enhanced We have developed a theoretical model based on TCMT for LSPRs coupled with Rayleigh anomalies (TCMT-RA) TCMT-RA is used for analyzing the spectra of nanodot arrays with various periods and dot sizes We calculate the reciprocal of external quality factor which means the percentage of LSPR energy radiating to far field per oscillation cycle and find that the value is universally proportional to the nanodot coverage The Rayleigh anomalies have four effects on the LSPR spectra namely redshift of LSPR asymmetric line shape bandwidth reduction and increased phase slope The results show that the decrease in the size-to-period ratio of nanodot array enhances the effects of Rayleigh anomalies

Date of Award	2014 Feb 11
Original language	English
Supervisor	Chun-Hung Lin (Supervisor)