Study on angle- and wavelength-dependent far-field scattering of a single nanostructure

Abstract

This thesis presents studies on wavelength- and angle-dependent scattering of a single optical nanostructure. First, using the finite-difference time-domain (FDTD) method, the near- and far-field characteristics of a single Au nanodisk coupled with a single dipole emitter were investigated. The Au nanodisk supports the dipole and quadrupole modes in the visible wavelength range. The power flow from the emitter-coupled Au nanodisk was systematically explored concerning the Poynting vectors of the total- and scattered-fields and the emitter output field. Second, the angle-resolved far-field scattering spectroscopy was introduced. Using this setup, angle- and wavelength-dependent far-field scattering/extinction distribution of a single Ag nanowire was measured. It is experimentally and theoretically revealed that the Fabry-Pérot resonance of excited surface plasmon on the nanowire as well as the phase matching condition between the surface plasmon and the free-propagating radiation determines the far-field scattering and extinction distribution of the plasmonic Ag nanowire. The angle-and wavelength-dependent far-field scattering distribution enables to extract the intrinsic dispersion relation of the surface plasmon without any perturbation. Third, the multipolar characteristics on scattering distribution of a high-refractive index dielectric nanostructure supporting electric and magnetic multipole moments were investigated. The contribution of the individual multipole moments to the far-field scattering of a Si nanowire and Si truncated cone was experimentally measured and theoretically understood.