Effects of Rotation-angle on Surface Plasmon Coupling of Nanoprisms
Date Issued
2016
Date
2016
Author(s)
Chien, Miao-Hsuan
Abstract
The effects of rotation angle on the surface plasmon coupling of nanoprisms were analyzed using finite-difference time-domain simulations and were first verified experimentally through both near-field and far-field optical techniques in present study. In addition to the widely-discussed dipolar resonance in regular bowtie nanostructures, defined as tip-mode resonance in present study, the excitations of edge-mode resonance were discovered under certain rotation angles of nanoprisms. The transitions between modes also took place during rotations. To justify the theoretical predictions, the gold bowtie nanoantennas were fabricated with different rotation angles using electron-beam lithography with highly controlled geometries of nanostructures, and two different excitation wavelengths were used as incident sources of Raman spectroscopy on fabricated rotated bowtie nanostructures with different rotation angles, to provide near-field evidences for the excitation and evolution of different resonance modes. The dark-field scattering microspectroscopy was also adopted for the detection of the far-field responses. Based on the discovered trend, a plasmon protractor was created with the near-exponential decay relationship between the relative resonance wavelength shift and cosine of the rotation angle. A plasmon hybridization model was also proposed for rotated bowtie to explain the coupling between nanoprisms during rotation.
Subjects
Finite-difference time-domain method
Localized surface plasmon resonance
Plasmon coupling
rotation
Nanoprism
Bowtie
Surface-enhanced Raman spectroscopy
Type
thesis
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