Metasurfaces with plasmon-enhanced birefringence and polarization rotation
Kim, Young Hwa
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Metasurfaces are surface metamaterials and they can be configured to manipulate the optical polarization. In this thesis, the effects of plasmon-enhanced birefringence in producing polarization rotation are studied. The research works introduce and demonstrate novel designs of the sub-wavelength chiral metasurfaces utilizing plasmonic enhancement to produce giant polarization rotation. Chapter 1 serves as the introduction, as it briefly introduces the principles that are covered in the research. Chapter 2 is the theory chapter that discusses the electromagnetic theories that are involved in the proposed metasurfaces in final chapter. Chapter 3 presents the computational analysis of the proposed metasurfaces with different metamolecule structures. The methods are proposed to obtain giant polarization rotation using metasurfaces formed from planar arrays of metamolecules that consist of achiral plasmonic nanostructures encapsulated within a chiral-patterned lossless dielectric layer. At plasmon resonance, the sub-wavelength nanoinclusions produce enhanced polarization of the surrounding dielectric, which gives rise to polarization rotation in the transmitted field. Full-wave electromagnetic analysis is used to investigate the optical response of various media as a function of the symmetry and spacing of the metamolecules. The analysis shows that the metamolecules can be configured to produce frequency selective and polarization sensitive giant polarization rotation exceeding 1e5 deg/mm in the visible to near-infrared spectrum with relatively low loss. The proposed method opens up opportunities for the development of versatile ultra-thin media that can manipulate the polarization state of light for novel micro-optical applications.