Artificial metamaterials have attracted much attention in the last decade due to their unprecedented optical and thermal properties beyond those existing in nature. The proposed thesis aims at manipulating the light propagation in unprecedented ways and enhancing the near-field radiative heat transfer by employing metamaterials.
In this proposal, we investigated extraordinary transmission, negative refraction, and tunable perfect absorption of infrared light. A polarizer was designed with an extremely high extinction ratio based on the extraordinary transmission through perforated metallic films. The extraordinary transmission of metallic gratings was demonstrated to further increase if a single layer of graphene is covered on top. The physical mechanism is attributed to the excitation of a localized magnetic resonance. Metallic metamaterials are not the unique candidate supporting exotic optical properties. Thin films of doped silicon nanowires are demonstrated to support negative refraction of infrared light due to the presence of hyperbolic dispersions. Long doped silicon nanowires exhibit tunable perfect absorption.
In addition to far-field properties, the near-field radiative heat transfer can also be mediated by metamaterials. All substances above zero Kelvin emit fluctuating electromagnetic waves due to the random motions of charge carriers. Bringing objects with different temperature close can enhance the radiative heat flux by orders of magnitude beyond the Stefan-Boltzmann law. Metamaterials provide ways to make the energy transport more efficient. Very high radiative heat fluxes approaching to the theoretical limit were theoretically demonstrated based on carbon nanotubes, nanowires, and nanoholes by using effective medium theory. The quantitative application condition of effective medium theory was presented for metallodielectric metamaterials. Then, a further step is made to investigate one-dimensional and two-dimensional gratings based on exact formulations including the scattering theory and Green’s function method.