| Recently,terahertz has attracted lots of attention among scientific researchers,as an emerging technology and science in the field of electromagnetic wave.The research,with regard to terahertz sources,terahertz detectors,terahertz modulators and so on,is experiencing a flourishing development.Research on terahertz absorbers is one of these important research directions as well.Although scientific research on terahertz absorbers has been widely and deeply explored,limited by the lack of materials able to respond in the terahertz regime,there still remains various space to deplore.The thesis based on 3D graphene networks and metamaterial,puts forward several novel terahertz absorbers by theoretical calculations,numerical simulations and experimental measurements,which can be divided into three projects as follows:(1)Research on absorption properties of porous materials with 3D graphene networks.As for absorption properties of porous materials,making contrast between metal foams and porous materials with 3D graphene networks,the work found that 3D graphene networks can have an enhancement on terahertz absorption in porous materials.Through the unit-cell construction of a tetrakaidekahedral model,simulations were carried out that reasonably reproduced the experimental results.Meanwhile,theoretical calculations based on the transmission line theory were applied to compare with the tetrakaidekahedral model,giving consistent and reasonable results.Furthermore,the work forecast the ultra-band and high-efficiency terahertz absorbing ability of the three tested porous materials in higher frequencies through numerical simulations.(2)Design and research on actively-controlled terahertz absorbers with temperature-sensitive semiconductor.Based on the multiple beam interference theory,the work designed a terahertz absorber with an ultrathin sandwich-structured system.Using the properties of thermal-tunable variation on intrinsic carrier density in InSb,the work developed the terahertz absorber with an ultrathin dielectric film into an actively-controlled absorber.In numerical simulations,this active tunability shows polarization insensitivity and high tolerance of incident-angle.(3)Design and research on actively-controlled terahertz absorbers by optical pump.Using the properties of isolator-metal transition in optically-pumped silicon,the work put forward an actively-controlled terahertz absorber to accomplish the function of on-to-off absorption,based on the typical structure system of metamaterial absorbers.By numerical simulations,the findings are as follows:(1)The function of active control can be improved by increasing pump power and choosing appropriate pump wavelength.(2)The shelter of metal resonators from optical illumination would impair the absorption of this absorber,which can be improved by increasing the effectively-pumped depth in silicon.(3)The proposed actively-controlled absorber can keep a stable performance at various incident angles under different electric polarization modes. |
