Research On Terahertz Array Device Based On Reconfigurable Artificial Microstructure

Terahertz(THz)waves have attracted much attention due to their application value in communication,imaging,and biology.Limited by terahertz feed power,atmospheric attenuation,terahertz antenna gain,etc.,both terahertz imaging systems and wireless communication systems urgently need a dynamic beam reconfigurable mechanism with high spatial resolution and direction adaptive tracking with large field of view coverage.At present,the terahertz beam reconfiguration technology is the focus of terahertz technology.With the development of terahertz photonics and solid-state source devices,it is required that the reconfigurable system with multi-band and multi-mode should be integrated,fast and flexible at sub wavelength scale.In this dissertation,the fundamental properties of electromagnetic waves,such as frequency and polarization state,are taken as the reconstruction conditions,and the reconfiguration of terahertz beams is realize by combining artificial microstructure arrays(Metamaterials,Artificial Electromagnetic Medium).The hybrid structure composed of high electron mobility transistor(HEMT)and artificial microstructure is used as the coding unit cell to manipulate the THz beam dynamically.On the basis of theoretical analysis and simulation,samples are processed and verified by experiments.The main achievements and innovations of this dissertation are as follows:1.An electromagnetic dual-mode resonant artificial microstructure with a broadband response and orthogonal polarization response is proposed.These two electromagnetic resonance modes broaden the operating bandwidth of artificial microstructures and improve the phase shift linearity in the nearly 200 GHz band.Combined with the orthogonal polarization response characteristics,an anisotropic artificial microstructure with electromagnetic dual-mode resonance is constructed,which has different phase responses to orthogonally polarized electromagnetic waves.Enriched the reconfiguration method of terahertz artificial microstructure array.2.From the generalized Snell's theorem,the ability of metasurface to deflect electromagnetic beams at different frequencies and phase gradients is deeply explored.A design method for maximum scanning angle of metasurface in a given frequency range is presented.A terahertz frequency reconfigured metasurface based on an electromagnetic dual-mode split ring resonators is constructed and developed.The simulation and experimental results show that the maximum scanning angle is 40 degrees in the frequency range from 0.3 THz to 0.5 THz.The reliability of the design method of terahertz frequency reconfiguration metasurface for obtaining the maximum scanning angle is verified.3.Aiming at the problems that traditional isotropic artificial microstructure metasurfaces can only respond to a single polarized electromagnetic wave and have unique functions,a method of constructing polarization reconfiguration artificial microstructure metasurfaces based on an anisotropic phase matrix is proposed.Based on the polarization state of the terahertz wave,one-dimensional and two-dimensional polarization anisotropic phase matrix metasurface are designed.In the frequency range of 0.32 THz to 0.42 THz,the simulation and experimental results show that the polarization beam separation in the same plane with different angles is realized when the orthogonal polarized electromagnetic wave incident on the one-dimensional metasurface.In the two-dimensional case,the polarization separation of the orthogonal plane is realized,and the maximum reflection coefficient is 78%.It is proved that the artificial microstructure array constructed by the anisotropic phase matrix has various reconfiguration functions for different polarized incident electromagnetic waves.The research results have important value in the application fields of multi-channel wireless communication system and holographic imaging.4.The dynamic reconfiguration of the terahertz beam is realized for the first time in China by adopting a 32 channel 1-bit programmable array composed of HEMT.The programmable unit effectively combines the electronic transport characteristics of the two-dimensional electron gas in HEMT with the resonance characteristics of artificial microstructures and achieves 180 ° phase modulation in the frequency range of 80 GHz.Experimental results show that the programmable array can realize the dynamic manipulation of the incident beam in the frequency range of 0.33 THz to 0.38 THz.The main lobe amplitudes obtained at 0.358 THz are 0.81 and 0.75,and the angles are-39 ° / + 37 ° and-30 ° / + 28 °,which are basically consistent with the simulation and theoretical results.This work is of considerable significance to promote the development of terahertz high frame rate high-resolution imaging and high-speed wireless communication.