Design And Simulation Of Electromagnetic Metamaterial Absorber Structure

Metamaterials generally refers to a class of artificial composite structures possessing superior physical properties that natural materials do not have. The equivalent dielectric constant and magnetic permeability, resultantly properties, of metamaterials can be adjusted by designing specified structures. The related researches have become a interdiscipline frontier involving in physics, material science, engineering, chemistry and so on. As one of very prominent applications of metamaterials, absorbers based on metamaterials are becoming ones of the best choices of many novel applications due to near unity absorptance at specific wavelength. Since its first experimental demonstration in 2008, many novel metamaterial absorber structures have been proposed in the range from microwave to infrared, even visible spectrum.This thesis briefly introduced the concept, progress and applications of metamaterials and metamaterial absorbers. Then basic theory for the design, analysis and characterization was elaborated. And then two different absorbers: metamaterial absorber and ultra-narrow band absorber, were proposed and analyzed. The main work and the results are as follows.(1) A metamaterial absorber structure with three layers was designed. The optimized absorber structure has the absorptivity of 99.9% at 5.8 μm, and shows polarization-insensitive and wide-angle optical properties. Especially, the metamaterial absorber also has excellent tunability. The resonant wavelength can be tuned between 3.4 μm and 8.6 μm with the absorptivity above 95% by changing the dimension of the structure. Furthermore, the absorption mechanism was discussed and analyzed in detail. The near-unity absorption can be attributed to both the electric and magnetic resonances. The energy loss mainly results from the ohmic loss which occurs in the two metallic layers.(2) Based on the designed metamaterial absorber, the dynamical modulation of absorptivity can be realized by introducing VO2 with semiconductor-to-metal phase transition(SMPT). By replacing the material of top layer with VO2, the absorptivity can be modulated from about 2% to 99.8% before and after SMPT of VO2, and it has very wide absorption band under metal state of VO2. By replacing the material of bottom layer with VO2, one also can achieve the absorptivity modulation from about 16% to 96.4%.(3) An ultra-narrow band absorber was put forward. This absorber has near unity absorptance,and is polarization-insensitive and wide-angle. This specially-designed absorber shows an utlra-narrow FWHM(full width half maximum), just 3.12 nm. The absorber is very sensitive to the refractive index of environment. According to the simulation results, the sensitivity and figure of merit of this absorber is 1423nm/RIU and 259/RIU, respectively, and the maximum FOM* reaches 2723. This indicates that the designed ultra-narrow band absorber may be an excellent sensor with very superior properties.