基于石墨烯-VO_(2)的可重构太赫兹超宽带吸波器

Ultra-Wideband Reconfigurable Terahertz Absorber Based on Graphene-VO_(2)

本文提出了一种基于石墨烯和二氧化钒(VO_(2))的伞状结构可重构太赫兹超宽带吸波器,极大地拓展了太赫兹吸波器的吸收带宽,具有功能可重构、调制深度大等优点.该吸波器由伞状VO_(2)贴片、聚乙烯环烯烃共聚物(To⁃pas)介电层、石墨烯层以及金属反射层组成.当VO_(2)处于绝缘态、石墨烯的费米能级为0 eV时,该吸波器在整个太赫兹波段内表现为全反射特性.当VO_(2)处于金属态、石墨烯的费米能级为0.75 eV时,该吸波器在3.57~10 THz频率范围内实现了超宽带吸收,平均吸收率达到了94%以上,吸收带宽高达6.43 THz.同时调节VO_(2)的电导率和石墨烯的费米能级,可在两个完美吸收点处实现最大分别为97.9%(4.3 THz处)、96.8%(8.25 THz处)的调制深度,具有良好的开关特性.此外,该吸波器还具有极化不敏感和广角吸收特性,在0°~35°的入射角范围内,该吸波器在3.57~10 THz带宽范围内均保持着90%以上的吸收率.该可重构太赫兹超宽带吸波器在可调宽带吸收器件、隐身器件、热探测、太赫兹开关等领域具有潜在的应用价值.

In this paper,a reconfigurable terahertz ultra-wideband absorber with umbrella structure based on gra⁃phene and vanadium dioxide is proposed,which greatly expands the absorption bandwidth of the terahertz absorber and has the advantages of functional reconfiguration and large modulation depth.The absorber consists of an umbrella shaped VO_(2)patch,a polyethylene cycloolefin copolymer(Topas)dielectric layer,graphene layer,and a metallic reflector.When VO_(2)is in the insulating state and the Fermi level of graphene is 0 eV,the absorber exhibits total reflection characteristics in the whole terahertz band.When VO_(2)is in the metal state and the Fermi level of graphene is 0.75 eV,the absorber achieves ul⁃tra-wideband absorption in the frequency range of 3.57~10 THz,with an average absorption rate of more than 94%and an absorption bandwidth of up to 6.43 THz.By adjusting the conductivity of VO_(2)and the Fermi level of graphene at the same time,the maximum modulation depth of 97.9%(at 4.3 THz)and 96.8%(at 8.25 THz)can be achieved at the two perfect ab⁃sorption points,which has good switching characteristics.In addition,the absorber has polarization insensitivity and wideangle absorption characteristics.In the range of 0~35°,the absorptivity of the absorber is more than 90%in the range of 3.57~10 THz bandwidth.The ultra-wideband reconfigurable terahertz absorber will have potential applications in tunable broadband absorber,stealth devices,thermal detection,terahertz switches and other fields.