| The terahertz waves are in the frequency range of 0.1-10 THz with the advantages such as low photon energy,high penetration capability and large information bandwidth capacity,which have significantly broad application prospects in security detection,communication,imaging and radar fields.The terahertz band is also known as the unique "terahertz gap" in the electromagnetic spectrum due to the lack of low-cost,compact and room-temperature emission sources and detector devices.In recent years,with the development of high-frequency signal sources such as Schottky diode frequency multiplexer,Gunn diodes,quantum cascade lasers and ultrafast lasers,terahertz technology has moved towards applied researches such as the regulation of the transmission,reflection,absorption,polarization and other characteristics of terahertz waves.The regulation of terahertz waves is one of the cores of terahertz technology and plays an indispensable role in the terahertz system.However,the current terahertz modulation technology is still not mature with poor modulation performance,low cost performance,narrow operating frequency and other difficulties.One of the key technologies for terahertz wave regulation is metamaterial.As an artificial composite material with periodic structures,metamaterials can achieve negative magnetic permeability and negative permittivity which do not exist in nature,thus have the capacity to generate some unnatural wave-regulating properties.The dynamical regulation of metamaterials has been extensively studied in the optical and microwave frequency bands with diverse methods including using traditional electrical devices like varactor diodes and novel materials like graphene and molybdenum disulfide.However,in the "terahertz gap",the methods of dynamically regulating for metamaterials are extremely limited with ideal regulating performanceBased on the background mentioned above,two methods of dynamically regulating for terahertz metamaterials are proposed,prepared and tested in conjunction with semiconductor processing technology.The main contents are as follow:1.A method of using Indium Gallium Zinc Oxide(IGZO)Schottky diode to regulate Electric-LC(ELC)metamaterial is proposed.By growing IGZO with a Schottky contact as the capacitor of the ELC metamaterial,the resonance strength of metamaterials can be regulated by changing the electrical conductivity of IGZO through the bias voltage,so as to realize the dynamic regulation of the transmittance of terahertz waves with its ideal regulation limit up to 11 dB at 0.41 THz.2.A method of dynamically regulating terahertz metamaterial microcavity using piezoelectric crystal materials is proposed.The microcavity uses Electromagnetic Band Gap(EBG)metamaterials as the reflective surface to achieve high-Q abnormal transmission with the Fabry-Perot structure.By adjusting the distance between the two reflecting surfaces with employing bias voltages to the piezoelectric bimorph,the frequency of abnormal transmission can be regulated in a wide range.When bias voltage is in the range of-30V to 30 V,the resonance frequency can be continuously adjusted between 0.35 and 0.5 THz with a Q factor as high as 750. |
