Flexible Terahertz Metamaterial Absorber

Terahertz and metamaterial was two major burgeoning technology at the end of last century. After exploring almost every domain of the electromagnetic spectrum, the only left terahertz gap was taken seriously by more and more scientists. Metamaterial has become a good candidate for exploring the terahertz band due to its novel electromagnetic characteristics, artificially adjustable capability. Metamaterial can remedy the insufficiency of functional materials and devices at the terahertz band. In this paper, we focus on metamaterial absorbers in terahertz regime with flexible dielectric substrate.First of all, we did some necessary carding work on theory and implementations of metamaterials which were applied to absorbing electromagnetic wave energy. After that, we proposed several metamatrial absorber designs which have simple geometry metallic periodic structures, and conducted full wave simulations of these metamaterials utilizing simulation software CST. By optimizing structure parameters, the designs can absorb more than 90% polarized or unpolarized terahertz wave energy at one frequency point or multi frequency points.Secondly, we have utilized microfabrication and free standing flexible polyimide substrate to fabricate these metamaterial absorber samples. We measured the reflection of these samples on a plane substrate with terahertz time-domain spectroscopy, in order to calculate the practical absorption spectrum. The experimental results are consistent with simulation results, which demonstrates that our designs achieve high efficiency absorbing ability in terahertz regime. Among these designs,the metamaterial absorber with multi resonate unit cells composed of four circular metallic plates was demonstrated to have polarization insensitive, wide incident angle, broadband(simulated FWHM reached to 45.6%) absorptionFinally, we probe into the flexible absorber’s ability of enhancing the sensitivity of bolometer, and the ability of reducing RCS of curved surface, under simulation environment. The results of the latter reveals that when comparing the metallic cylinder with metamaterial absorber to that without it, monostatic RCS reduction was approximately 90%, and total RCS reduction was approximately 37% around 0.63THz.