Terahertz Active Modulator Based Upon Metamaterial Coupling

Due to its unique physical properties,terahertz wave,previously known as "terahertz gap",has now become the focus of research for many scholars.These excellent properties merit its great application prospect in many fields such as medical treatment,communication,national security and nondestructive testing.To implement these applications,relevant theories and electronic components must be developed to realize the transmission,detection,modulation and absorption of terahertz waves.The modulation of terahertz wave is one of the important bottleneck of terahertz wave technology.The main reason that hinders the development of terahertz devices is the weak interaction between terahertz waves and substances existing in nature,which make it difficult to find suitable natural materials for terahertz devices.To solve this problem,artificial terahertz metamaterials with tens of microns in size are often used in terahertz wave modulators to enhance the interaction between terahertz wave and materials.The electromagnetic response of terahertz metamaterials is not only sensitive to the size,shape and dielectric environment of metamaterial,but also to near-field coupling between metamaterials.In this thesis,two type of metamaterials modulator were designed and realized by controlling the near-field coupling between terahertz metamaterials and the phase transformation of vanadium dioxide.Through electromagnetic simulation by CST software,the transmission spectrum,electric field and surface current were analyzed.The fabricated sample was tested using Fico terahertz time-domain spectroscopy system by applying voltage and temperature stimuli to perform active modulation of terahertz wave.In the system composed of C-type ring dimers and metal strip,electromagnetic induced transparency was realized before the phase transformation of vanadium dioxide due to introduction of metal strips.After the phase transition of vanadium dioxide,the resonance mode was switched to achieve transmission of down to 20.2%.In the system composed of U-type ring dimers and metal strip,the introduction of metal strips not only changes the resonant mode of U-type ring dimers from dipole resonance to magnetic dipole resonance,but also realizes electromagnetic induced transparency after phase transformation of vanadium dioxide.By comparing the different electromagnetic response of metamaterials dimers with and without introduction of metal strips,it is not difficult to find that the interaction between metamaterials can effectively change the terahertz wave modulation performance.This work provides a new method for the future terahertz metamaterials research for terahertz modulator,which has a very good development potential.