Manipulation Of Electromagnetic Wave Based On Plasmonic Metamaterials

The interaction between electromagnetic wave (EMW) and the matter has been extensively explored in a long time. Numerous optical components have been designed and developed to harness the EMW. With the development of advaned fabrication technology and material science in recent years, surface plasmon polaritons (SPPs) and metamaterials extend the range and enhance the interaction efficiency of EMW-matter interaction. Initially, the electromagnetic coupling is enhanced by the electric or magnetic resonances, resulting in the local field enhancement. Secondly, since electric and magnetic resonances can be tailored simultaneously, some intriguing electromagnetic properties which cannot be found in nature, such as negative/zero/high refractive index materials, can be obtained. Ultimately, SPPs and metamaterials bring many abnormal phonmona, such as extraordinary optical transmission (EOT), super-resolution imaging and electrometric cloak, which are believed to be impossible in the past.In this dissertation, we investigate the physical mechanism, numerical model, simulation and experiment characterization of the electromagnetic wave manipulation based on SPPs and metamaterials. The contents invole transmission, resonance, filting and splitting in plasmonic waveguide systems and high efficiency absorption, polarization conversion, and wave-front manipulation. The main original work and valuable results of this dissertation are as follows:1. In order to guarantee the generated SPPs travel in the desired direction and be splitted with a certain proportion, a plasmonic splitter consisting of the input waveguide, a slot cavity and output waveguides is proposed and numerically investigated using finite-difference-time-domain (FDTD) methods. Results show that resonant modes in slot cavity have different symmetries:the first order resonant mode is odd symmetry while the second order is resonant mode even symmetry. By varying positions of output waveguides, frequency splitter and 1×N (N= 2,3,4) power splitter can be achieved by the proposed structure. Output power ratio can be adjusted by changing the coupling distance and the refractive index of output waveguides. Besides, we present an ultra-broadband metamaterial absorber in the terahertz regime based on the proposed M × N cascaded metal-dielectric pairs, which consists of M super-unitcells with different lateral sizes w. Each super-unit cell is constructed by N subunit cells that are metal-dielectric pairs with the same lateral size but different refractive index. Numerical results showed that absorptivity of?92% was obtained between 3.2 and 11.8 THz using the 4 × 4 combination.2. In terms of spectral manipulation, we propose a plasmonic filter with a notch located along a rectangular resonator. The introduction of the notch affects the first and second resonant modes of the resonator in different manners due to different magnetic field distributions inside the resonator. The evolution of the transmission-peak wavelengths as a function of the notch position is given. The relationship between geometrical parameters of the notch and peak wavelengths is also studied. In addition, we investigate a plasmonic waveguide system based on side coupled complementary split-ring resonators (CSRR), which exhibits electromagnetically induced transparency (EIT)-like transmissionat visible and near-infrared region, simultaneously. The electromagnetic responses of CSRR can be handled by changing the asymmetry degree of the structure.3. We propose two-dimensional dispersion engineering to circumvent the bandwidth limitation of metamirrors, which are composed of a thin metasurface separated from a grounded plane with dielectric layer. Equivalent impedance theory and transmission line theory are utilized to establish the analysis model of dispersion management. Lorentzian resonances are exploited as building blocks in both dimensions of the dedicatedly designed meta-atoms to construct the expected dispersion. We validated this strategy by designing and fabricating anisotropic metamirrors, which can accomplish achromatic polarization transformation byond 2-octave bandwith. The underlying physical mechanism of dispersion engineering was explained in effective medium theory (EMT) and equivalent circuit model.4. With respect to the wave-front engineering, we propose the design of a planar dielectric metasurface as a compact orbital angular momentum (OAM) generator. The proposed metasurface is composed of annular subwavelength gratings, which can be taken regard as a space-variant Pancharatnam-Berry phase optical element, where the spin-orbit-interaction occurs. Consequently, the OAM-carrying beams with topological charge l= ±2 is generated with the efficiency high up to 90%. In addition, we demonstrate a method to produce fractional (l= ±1.5 and l= ±2.5), quasi-focusing, and quasi-non-diffracting OAM-carrying beams by adopting appropriate width modulation of the annular gratings, where the geometric phase retardation and propoagtion phase retardation superimpose with each other.