With Electrical And Magnetic Properties Of Radial Anisotropy Of The Nanoparticle System

The electromagnetic properties of nanoparticles with radial anisotropy are investigated in this thesis. We find that radial anisotropy can significantly affect the electromagnetic properties of spherical and cylindrical nanoparticles. For instance, the local field near the surface of the particle and the field amplitude between two particles can be enhanced or decreased by adjusting the components of radially anisotropic permeability and permittivity. As a consequence, it is believed that radial anisotropy can be used as an alternative freedom to control the electromagnetic properties of the particles. Our results and conclusions may become a theoretical guide of related experiments and device designing. The thesis is organized as follows:I. Light scattering and surface plasmon resonance of cylindrical particles with radial anisotropyWe generalize the full-wave electromagnetic scattering theory to study scattering of cylinders with radial anisotropy for normally incident light with transverse magnetic (TM) polarization. By taking into account the radial anisotropies in both the permittivity and permeability tensors, the scattering coefficients are exactly derived. It is shown that the surface and volume plasmon resonances can be identified by the sign of d ? t/dq, in which ? t is the permittivity element in a direction? , and q is the size parameter. The near field distribution differences between the two modes are illustrated by finite element method (FEM) simulation. Moreover, in the scattering efficiency spectrum with small q, the quadrupole and octupole resonant peaks may be much higher and sharper than that of dipole resonance. To one's interest, a tiny perturbation in radial anisotropy results in a strong switching of scattering diagrams in the vicinity of surface plasmon resonances.II. Study on near-field amplitude for plasmonic coated nanorods pair with radially anisotropic coresElectromagnetic scattering field amplitude in a pair of coated nanorods is investigated by finite element method. The coated nanorod is composed of a radially anisotropic dielectric core and a metallic shell. Numerical simulations show that for a given radial permittivity component ? r, with increasing the tangential permittivity component ? t, the surface plasmon resonant near-field amplitude is decreased, accompanied with slight red-shift of the resonant wavelength. On the other hand, with increasing ? r, the resonant wavelength exhibits significant red-shift, while keeping the maximal magnitude for isotropic case. Moreover, the effect of ? r is significant on the near-field magnitude when tuning the shell thickness. Furthermore, a compensating effect for the decay of the intensity with the increase of the gap width can be realized by manipulating the anisotropy of the dielectric core.III. Strong hybridizations between localized surface plasmons and anisotropic molecular shells in different orientation in a coated metallic sphereThe optical properties of a spherical plasmonic particle coated by anisotropic molecular layer are investigated by full-wave electromagnetic scattering theory. We discuss two cases that molecule resonance axes are oriented parallel or perpendicular to the coating normal. For small particle, we can observe the hybridization between the dipole resonance and molecular resonance, and there are two frequencies: low-energy frequency and high-energy frequency. The separation between the two frequencies is enlarged with increasing shell thickness. For large particle, multipolar hybridization between the localized plasmonic resonances and molecular resonances can be observed. The molecular shell thickness significantly affects the separation between low-energy frequency and high-energy frequency, as well as the peak values respectively.