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Title: Subwavelength manipulation of light via low-loss metamaterials
Author: Ma, Zhijie
ISNI:       0000 0004 7658 2246
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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Metamaterials are artificial materials with properties not found in nature, e.g. negative refractive index. However, the applications of metamaterials have been hindered by the inherent Ohmic loss in the metallic components. In this thesis, the possibilities of using low-loss dielectric metasurfaces and spoof plasmon surfaces to avoid the absorption loss have been investigated through both numerical and experimental studies. The controls of multiple light properties by these low-loss metamaterials are demonstrated. In the first part, an all-dielectric metasurface made of silicon resonator on insulator is designed and fabricated. By tailoring the electric and magnetic dipole modes in the dielectric resonators, a controllable phase range of 2π with high reflectance is achieved. Special beam generators of vortex beam and Bessel beam are numerically demonstrated in the reflection mode with high efficiency by the metasurface. Following that, an anisotropic dielectric metasurface is demonstrated, which functions effectively as an efficient reflective half-wave plate. Furthermore, local geometric phases can be imparted in the metasurface by simply changing the orientation of the resonator. In the second part, a dielectric planar chiral metasurface is studied. A Z-shaped dielectric resonator with broken in-plane mirror symmetry is designed to achieve giant optical chirality that breaks the limit in planar metallic structures. In addition, the circular polarization-selectivemetasurface converts the transmitted light into orthogonal polarization, with a geometric phase depending on the unit orientation. The chiral metasurface effectively integrates the functions of multiple optical components into a single piece. A computer generated hologram is demonstrated numerically as a proof of concept. In the last, a spoof surface plasmon waveguide is explored to achieve significant electric field confinement and enhancement at terahertz frequencies without inducing great loss in the structure. This greatly enhanced interaction between THz waves and matter is explored for sensing applications.
Supervisor: Maier, Stefan Sponsor: National University of Singapore
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral