超薄柔性透射型超构材料吸收器

设计并加工了一种超薄柔性透射型吸收器,总体厚度为0.288 mm,可实现柔性弯曲,容易做到与曲面目标共形.该吸收器由三层结构组成,底层是金属光栅,中间为介质层,表面单元由两条平行放置的尺寸不同的金属线组成.仿真和实验结果表明,对横电波在5和7 GHz的吸收分别达到97.5%和96.0%,对横磁波在3.0—6.5 GHz都能保持90%以上的透射率.两个吸收频点可分别独立调节,增加了设计的灵活性.另外,当入射角增大到60°时,该吸收器的性能基本不受影响,表现出良好的广角特性.

Ultrathin flexible transmission metamaterial absorber

As an important branch of metamaterial-based devices, metamaterial absorber (MA) has aroused great interest and made great progress in the past several years. By manipulating the magnetic resonance and the electric resonance simultaneously, the effective impedance of MA will match the free space impedance, thus resulting in a perfect absorption of incident waves. Due to the advantages of thin thickness, high efficiency and tunable property, MA has been widely concerned in energy-harvesting and electromagnetic stealth. Since the first demonstration of MA in 2008, many MAs have been extensively studied in different regions, such as microwave frequency, THz, infrared frequency and optical frequency. At the same time, the absorber has been extended from the single-band to the dual-band, triple-band, multiple-band and broadband. In recent years, the dual-band absorber has received significant attention and has been widely studied. So far, however, most of MAs are composed of a bottom continuous metallic layer, which prevents electromagnetic waves from penetrating and makes electromagnetic waves absorbed or reflected. In this paper, an ultrathin flexible transmission absorber with a total thickness of 0.288 mm is designed and fabricated, which can be conformally integrated on an object with a curved surface. The absorber consists of three layers of structure:the bottom is a one-dimensional grating type metal line, the middle is the medium layer, and the surface metal layer is composed of two different sizes metal lines in parallel. Simulation and experimental results show that the absorptions of TE wave are 97.5% and 96.0% respectively at the two frequency points of 5 GHz and 7 GHz. The transmission of the TM wave above 90% is maintained from 3 GHz to 6.5 GHz. We also simulate the spatial electric field distribution and magnetic field distribution at two resonant frequencies, and explain the electromagnetic absorption mechanism of the proposed structure for TE wave. Secondly, when the incident angle increases to 60 degrees, the performance of the absorber is substantially unaffected, exhibiting good wide-angle characteristics. In addition, through the analysis of structural parameters, two absorption peaks of the proposed absorber can be independently adjusted, resulting in a flexible design. In conclusion, we propose both theoretically and experimentally a polarization-controlled transmission-type dual-band metamaterial absorber that can absorb the TE waves and transmit the TM wave efficiently, which has important applications in the case requiring bidirectional communication.