| In recent years,with the gradual improvement of the micro-nano processing technology,it has become possible to construct a composite artificial medium-metamaterial that does not exist in nature.The unit cell of metamaterial can be artificially designed and brings us many specific and novel physical properties,such as negative refraction.This unique design concept has quickly become a research hotspot at home and abroad.The recent research on two dimensions metamaterials-metasurfaces driven from three dimensions metamaterials,has also attracted the attention of many researchers.The thickness of metasurface is generally on the order of sub-wavelength,making the system lighter and easier to assemble and integrate.So,metasurfaces can be applied to a variety of optical devices and has now set off a new research boom.The main contents of this thesis are as follows:(a)Based on the researches about electromagnetically induced transparency(EIT),we first present a classical analog of electromagnetically induced transparency based on an isotropic metasurface with double rings.Under the excitation of incident light,two opposite current is excited to flow at those two rings.Then the interference between them forms an EIT phenomenon.Then we propose another controllable isotropic EIT analog based on metasurface which consists of four metal split rings and a metal cross.By adding a phase-transition material,vanadium dioxide,under the metal metasurface and then adjusting the conductivity of the vanadium dioxide,a dynamically adjustable EIT phenomenon can be realized.Therefore the utilization rate of this designed device is improved.Those two devices both are designed to have wide-angle characteristics and are insensitive to polarization.(2)Based on the researches about metallic polarization rotator,we demonstrate a reflective linear polarization rotator in wide band(4.9 GHz-10.4 GHz)by rationally designing the metallic grating metasurface and selecting the appropriate metal line width and period.This designed system has the advantage of wide-angle feature.(3)Based on the researches about polarization beam splitter based on metamaterials,we propose a polarization beam splitter by exciting plasmonic magnetic resonance in this system,so that the completely optical opaque metal is transparent to the y-polarized incident wave while it is still completely opaque to x-polarized incident wave.(d)Based on the researches about dielectric reflector,we present a broadband terahertz dielectric reflector by exciting separated Mie resonance(magnetic resonance and electrical resonance)in high refractive index titanium dioxide(V02)particles.Thereby a broad reflection band in the range of 0.83 THz to 0.96 THz is realized.The designed structure consists of only a single layer of V02,making it easy to fabricate and possible to avoid ohmic losses. |
