Research On Water-Graphene-Vanadium Dioxide Tunable Metamaterial Absorbers

Metamaterials provide new applications for manipulating electromagnetic waves due to their extraordinary electromagnetic properties,and with the continuous research of wave absorbers,the use of metamaterials to build terahertz absorbers has gradually become a research hotspot.Most of the terahertz absorbers designed today are single-band absorbers with high efficiency or multi-band absorbers with low efficiency,while reconfigurable multiband perfect absorbers with multi-band perfect absorption and reconfigurable absorption bands have potential applications in optical switches and modulators,etc.The value of reconfigurable multi-band perfect absorbers has received much attention.The use of tunable elements can actively control the absorption rate and operating frequency of the perfect absorber,in nature water has a high dielectric constant and excellent frequency dispersion characteristics,is a natural absorber,and its temperature-controlled properties add to the absorption band tunability of the absorber,graphene high absorption coefficient and controlled conductivity and other excellent physical properties,so that the absorption function and tuning absorption band in the terahertz band is possible.Vanadium dioxide is a solid material with phase change properties,and combining multiple tunable elements to build absorbers enriches the modulation means and absorption effect.In this thesis,two different reconfigurable terahertz absorbers are designed based on the tunable elements water,graphene,and vanadium dioxide,respectively,and the main research can be summarized as follows:1.We design a fully dielectric terahertz absorber based on aqueous graphene cascade metamaterials,using thermally controlled vanadium dioxide material to achieve perfect absorption switching between eight-band and four-band in the 0-3 THz frequency band,followed by introducing the electric field distribution of the absorber to analyze the absorbing mechanism of the structure.The influence of the structural parameters on the absorption effect of the absorber is then studied,and the variation curves of the absorber with respect to temperature and Fermi energy level of graphene are shown,and the absorption profiles of the structure are given for different incidence angles of TE and TM wave modes.The design is compared with the current literature to show the superiority of the design and the freedom of the design for a wide range of applications such as energy harvesting and electromagnetic wave manipulation.2.We propose a temperature-controlled and electrically-controlled reconfigurable singleband and dual-band water-based graphene metamaterial absorber,which utilizes the phase transition property of vanadium dioxide to achieve the perfect absorption at dual frequency points of 0.742 THz and 2.579 THz and the flexible switching of single absorption band in the frequency range of 1.497 THz-2.602 THz.The absorption mechanism of double-band absorption and single-band absorption are analyzed respectively with the electric field distribution of the absorber,and the influence of specific structural parameters on the absorption pattern of the absorber is studied.This absorber structure is of great reference value for the future design of terahertz reconfigurable absorbers.