Investigation Of Tunable Metamaterial Absorber In The Terahertz Band

Since the first metamaterial absorber(MA) was proposed by W. J. Padilla et al. in 2008, a variety of MA was designed, and the performance of MA has been improved greatly in recent years. Besides, many applications about MA have also attracted comprehensive attention, such as compressive imaging, frequency selective thermal emitter, detector and sensor etc. This paper investigated the theoretical mode of MA and several tunable MAs. The main content is listed as follows:(1)Two kinds of tunable metamaterial absorber based on graphene was investigated. In infrared band, the permittivity of graphene changes from dielectric to metal as the Fermi-level of graphene increase. Utilizing this special character of graphene, we achieved dynamic absorption frequency via combing metallic ellipse array with graphene. And the physical mechanism of tunability is well explained by bulk effective model. In terahertz band, through replacing metallic ellipse with graphene disk, a new amplitude tunable metamaterial absorber was proposed. And the modulation depth of this absorber is up to 137%.(2)A new resonant mode was investigated in conventional square ring structure. Through combing the new mode with the existing mode in square ring, we proposed a new dual-band MA. Moreover, utilizing some good properties of the permittivity of SrTiO3(STO) in 0.1-0.5THz, such as small dispersion, low tangential loss and controlled by temperature, a temperature-control frequency-tunable dual band MA was present. And the nature of frequency-tunable is well explained by bulk effective model.(3)As for conventional concentric multiple square ring structure, we discussed the resonant characters of every independent square ring and the whole structure when the material of metal is chosen as perfect electric conductor(PEC) and aluminum(Al) separately. Then, an absorption switchable MA was proposed through embedding Silicon(Si) slice in gap between the two square ring. The essence of switchable absorption peak is that the change of conductivity of Si makes two square ring coupled. Based on two square rings MA, a triple-band switchable metamaterial absorber was also achieved.