Study Of Polarization Insensitive Wideangle Multi-band Metamaterials Absorbers

Metamaterials are artificial materials which are engineered to exhibit extraordinary electromagnetic properties that have never been found in nature, such as negative refraction, negative group velocity. Potential applications of metamaterials are diverse, such as sub-wavelength imaging and optical stealth. When the impedance of the metamaterial matches to that of free space, it is possible to realize perfect absorption of specific frequency in the incidence electromagnetic waves through carefully designing of the size and the geometric shape of the unit cell. Metamaterial can be widely applied in many fields, such as THz imaging, thermal emitters, toxic substances detecting and solar cell.In this paper, we studied the absorption mechanism of single-band and multiband metamaterials absorber based on an ELCR in mid-infrared wavelength regime with the combining of numerical simulation method and theoretical analysis. Then we obtained the influence of geometric parameters and material electromagnetic parameters on absorption rate.We calculate the spectrum characteristics of the square sheet metal metamaterial absorber in mid-infrared wavelength regime, using the finite element method, based on the absorption theory of electromagnetic wave absorption and effective-medium theory. Single frequency perfect absorption can be achieved by adjusting the geometry parameters. Equivalent medium theory were used to give a comparison. The calculation of the resonant frequency of the two methods is consistent. We used the distribution of electric field mode to explain the physical mechanism.We studied the absorption properties of a kind of metamaterial absorber based on electric resonator. The absorber can realize multi-frequency, polarization independent perfect absorption in terahertz band. Then we designed a multiband frequency metamaterial absorber, which concludes an ELCR and a metal substrate. The structure can generate two perfect absorption peaks in mid-infrared band. The absorption rate is over 90% in the 12-24 THz. We used the electric field modes distribution and the surface current density to explain its absorbing mechanism.