Study On Radiation Mechanism Of Terahertz Antenna By Transmission Line Microstructure

Terahertz waves are generally defined as the electromagnetic waves in the frequency range of 0.1 to 10 THz.The development of terahertz devices is an important part to promote the research of terahertz techniques,in which the researches of terahertz sources are most essential.The terahertz photoconductive antenna emitter has the advantages of wide frequency band,high signal-to-noise ratio,low pump optical power,and compatible with fiber optics,thus is widely used in terahertz photonics research.The main challenge of current photoconductive(PC)antenna is the inability to regulate its spectrum.This significantly limits the practical application of PC antennas.In order to expand the function of the PC antenna as well as control the peak intensity and power distribution of the spectrum with high degree of freedom,a method of integrating the metal metamaterial microstructure into the coplanar transmission line of the PC antenna is proposed in this thesis.By adjusting the geometry,size,and position of the metamaterial microstructures,the spectral characteristics of the radiation from the PC antenna can be flexibly modulated.Inspired by the stub filter researches,several metamaterial microstructures were symmetrically added on both sides of the antenna gap,which are connected to the coplanar transmission line.Utilizing terahertz time-domain spectroscopy system,the metamaterial integrated PC antennas were experimentally characterized,in which the repeatable time domain and frequency domain spectra are obtained.By analyzing and comparing the experimental data and combining with the numerical simulation results,the influence of metamaterials on the antenna's far field radiation are summarized,the role of the metameterials in the spectrum characteristics of the antenna is clarified,and related numerical studies is carried out to take an insight into the underlying physics.The proposed design strategy of introducing the metamaterial microstructures to modulate the radiation spectrum of the PC antenna,which is flexible,effective,and expandable,would be a novel way for ultra-integrated,multi-functional terahertz sources.