| Terahertz spectrum communication can achieve excellent performance such as ultra-wide bandwidth and ultra-high transmission rate.With the layout of our country’s6G terahertz technology,the terahertz spectrum modulation functional device as the core of the system is currently an international frontier research field,with huge application requirements and research significance.However,the development of terahertz communication has long been limited by the lack of efficient frequency response materials and devices in the terahertz region.At present,the development requirements of terahertz metamaterials are excellent robustness,active tunability,and intelligent sensing.However,there are still problems such as poor flexibility in active modulation and high power-consumption,which cannot meet the new requirements of high-speed and green development of 6G communication.Aiming at many problems,the stability of the unit cell and the diversity of the system are improved according to the various control functions of metamaterials on physical parameters such as the amplitude,phase,and frequency of terahertz waves.The main research contents of this thesis are as follows:(1)A novel non-planar three-dimensional(3D)hemispherical metamaterial unit cell structure is proposed,which has a clear 3D structure and excellent beam steering properties in the terahertz region.Firstly,the transmission characteristics of 3D hemispherical metamaterial affected by various parameters are compared and optimized,and a band-stop filter around 2.37 THz is constructed using metamaterials.Furthermore,an encoded metamaterial array composed of 3D hemispherical unit cells is realized.Due to the excellent isotropy of the 3D hemisphere,the encoded array exhibits excellent robustness in the terahertz spectrum.Radar Cross section(RCS)analysis shows that it is insensitive to changes in the polarization mode and incident angle of the incident wave at 0.6-1.7THz.The 1-bit coding array can achieve more than 10 d B RCS reduction from 0.7THz to 1.4THz.And the RCS reduction can reach about 30 d B at 0.75 THz.(2)Aiming at the intelligent and actively tunable characteristics of metamaterials,this thesis innovatively proposes a concept and design method of low-carbon self-powered terahertz liquid crystal tunable metamaterials driven by triboelectric nanogenerator(TENG).Based on the idea of co-integrated design of TENG and liquid crystal metamaterials,the design methods of spectrally reconfigurable liquid crystal metamaterial systems are enriched.By integrating TENG,the changes in the terahertz spectral response properties of large-scale metamaterial arrays are driven by self-powering.A TENG in contact separation mode is fabricated,which could output an AC voltage of 50 V on the fabricated polymer dispersed liquid crystal(PDLC),which effectively changed the optical transparency of the liquid crystal film,and further analyzed the rationality of its work in the terahertz region.The finite element tool CST Microwave Studio is used for modeling and simulation,and the fabricated PDLC liquid crystal material is integrated with the metamaterial microstructure.The terahertz spectral response and electromagnetic resonance mechanism of metamaterial integrated nematic liquid crystals with a cross-shaped structure,a single split resonator structure,and a symmetrical double split resonator structure are respectively studied.Among them,the asymmetric cross-structured liquid crystal metamaterial can achieve an obvious0.02 THz spectral shift under the applied bias voltage.The design ideas of terahertz liquid crystal metamaterials are summarized,and the design method support is provided on the concept of self-powered tunable liquid crystal metamaterials. |
