| Recently, metamaterials have been a hot field in Physics, Chemistry, Biology and Medicine. Metamaterials show a lot of new phenomena, such as negative refraction, transformation optics, Fano resonance, plasmon-induced transparency and optical activity etc. Therefore, they have attracted worldwide attention in the scientific society.In this thesis, theoptical properties of metamaterials have been investigated both experimentally and theoretically, including influence on the optical properties of metamaterials due to the symmetry breaking of structure and modulation to the optical properties for the phase transition materials under variable temperature. Some significative results, such as Fano resonance, plasmonic analogue of electromagnetically induced transparency, optical activity, and the switched effect associated with the phase transition of vanadium dioxide, have been obtained.1) The optical properties of a composite metamaterial, composed of asymmetric split-ring resonators (ASR) inserted into the periodic circular holes, have been investigated both experimentally and theoretically. For the metamaterial with the interaction between the air cavity and ASR neglible, transmission peaks and dip associated with the localized plasmon excitations have been found:the peaks originate from the resonances of the smaller or bigger SRR, and the dip stems from the strong coupling between them. In addition, for the metamaterial with the interaction between the air cavity and ASR, transmission peaks and dip are red-shifted when the radius is decreased and the interaction is enhanced. To understand the results, a composite LC circuit model has been employed.2) In the traditional PIT metamaterials with metallic nanoparticles, the PIT-transmission peak increases with the enhanced coupling between the two plasmonic modes. We have demonstrated experimentally a plasmonic-induced-transparency (PIT)-like spectral response in a perforated planar metamaterial with hole and slit pairs. Unlike the traditional PIT metamaterials with metallic nanoparticles, the PIT-like transmission peak is modulated by interference between the composite diffracted evanescent wave and the direct transmission field. A new theoretical model of diffracted wave-enhanced transparency (DWET) has been proposed to reveal the underlying physics, which agrees well with the simulated results. Our structure may provide a new platform to obtaining low-loss optical metamaterials.In addition, the metamaterial with the overlapping between hole and slit pairs have been investigated. The results indicate the symmetric breaking leads to the split of the transmission peak. The LC model explains the phenomena of the experimental and the simulated result.3) The optical properties of a planar metamaterial with gammadion-shaped chiral symmetry breaking holes array has been investigated both theoretically and experimentally. The results indicate that the introduction of the chiral symmetry breaking causes the split of the transmission peak and exerts large influence on the optical rotation and circular dichroism. Our metamaterials might have potential applications in photography, life science microscopy, polarization controllers and circular polarizers.4) We have fabricated a metamaterial of metal/semiconductor/metal sandwich nanostrips structure comprising a pair of gold strips and a vanadium dioxide (VO2) strip. The optical response of the metamaterial has been studied. The results indicate the nanostructure with VO2 strips can be used as a temperature-controlling optical switch and the mechanism of this switch can be explained by the magnetic resonance.In addition, the optical properties of the fishnet metamaterials with the VO2 spacer have been investigated theoretically. The results indicate this metamaterial also can be used as a terperature-controlling optical switch and the mechanism of the switch can be explained by the FP resonant model. |
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