Research On Metamaterial Absorber

Metamaterials are artificial media structured on a size scale smaller than the wavelength of external stimuli, which have novel physical characters. Owing to their arbitrary effective electromagnetic parameters, metamaterials have been applied to make superlens, cloaking devices and perfect absorbers. In this thesis, metamaterial absorbers that work in microwave regime and terahertz regime are investigated.First of all, an ultrathin, wide-angle and polarization insensitive microwave low frequency metamaterial absorber is studied. The absorber is consisted of periodic arranged metal rings with metal strips. It achieves perfect absorption at2.56GHz and the ratio of its thickness to the wavelength is1/88. The mechanism of its ultrathin character is investigated carefully. Also, a sample is fabricated and measured.Secondly, an electrically tunable microwave metamaterial absorber is designed. With varactor diodes embedded between metamaterial units, The absorber can be tuned by changing the reverse bias voltage. The tunable width of the absorption frequency is about0.75GHz.Thirdly, an ultra-broadband terahertz metamaterial absorber is studied. This absorber is consisted of a periodic array of multilayered metal-dielectric pyramids. Simulated results show that the absorbance is higher than90%in the frequency range of1.08-2.15THz at normal incidence and its relative absorption bandwidth is66.0%. The mechanism of its ultra-broadband character is investigated carefully. And, a sample is fabricated and measured by terahertz time domain system.Finally, a brief summary of our investigations and some future research directions are given.