Metamaterial Absorbers And Left-Handed Metamaterials

Metamaterials, periodic sub-wavelength artificial materials, exhibit extraordinary electromagnetic properties not available in conventional materials, which have potential applications such as cloaking, nano-scale optical imaging, micro-resonators, directional antenna emitters, thermal detectors, solar converters, and bending waveguides.In this paper, in order to develop new types of metamaterials, we systematically investigated the triangle metamatenal absorber, the short-line zero-index metamaterial, the Rectangular-ambulatory-plane negative-index metamaterial, the double-E metamaterial, the square-line negative-index metamaterial, and the coin-shaped metamaterial. The calculation of equivalent parameters and the analysis of the relationship between structures and electromagnetic properties were performed. The microwave response mechanisms of these extraordinary electromagnetic properties were revealed. The focuses were mainly on the electromagnetic properties of the triangle metamaterial absorber and coin-shaped metamaterial.For the triangle metamaterial absorber, the thickness is about 1/8 wavelength, which is much less than that of conventional dielectric absorbers (A/4). Further, comparing to the conventional dielectric absorber, the metamaterial has superior absorption ability. The frequency of absorption peak is blue-shifted with the decrease of thickness, and it is linearly dependent on the slot width, which provides an easy way to manipulate the microwave absorption band. The power loss is mostly concentrated on the dielectric in the slots and sharp angles of triangles. The power loss is mainly contributed by the dielectric loss and supplement by Ohmic loss, so the absorber will be useful for developing applications such as thermal detectors, sensors, and microwave attenuators.The coin-shaped metamaterial is capable of realizing not only a negative-index band (figure of merit is 5.6) but also two zero-index bands (a broad band and a low-loss band), which has obvious advantages in multiband, multifunctional, different loss microwave devices. The relationship between the coin-shaped ring/wires and resonant frequency were explored deeply. The formulas for electric plasma frequency and magnetic plasma frequency were established respectively, and the mechanism of the negative refraction and zero refraction of the coin-shaped metamaterial were analyzed, providing reference for the research of metamaterials. Based on the results of zero index properties, a general criterion for zero refraction was proposed, i.e. to satisfy both ε’μ"+μ’ε"=0 and μ’ε’-ε"μ"<0, providing a theory of designing broadband zero-index metamaterials. Additionally, we discussed the applications of zero-index metamaterial in bending coaxial waveguide, T-shaped microstrip line, and horn antenna.