Studies Of Terahertz Modulator Based On Flexible Vanadium Diozide Film

Tahehez（THz）wave has the characteristics of strong penetration,low photon energy,and wide bandwidth,etc.,has important applications in the fields of aerospace,communication,security inspection.However,due to the limitations of THz,there are very few functional devices that can be applied to THz bands,especially efficient and fast THz modulators.Therefore,further promoting the development of VO₂-based active THz modulators to achieve excellent modulation performance requires new materials and design.In this paper,magnetron sputtering method is used to deposit VO₂ on ordered carbon nanotube（CNT）film and silicon nitride（SN）nanotube film substrate,and the preparation of flexible VO₂ film is successfully realized.VO₂ is compounded with ordered CNT film to design an actively adjustable THz modulator.The modulator combines the advantages of two materials and has the characteristics of flexibility,multiple modulation methods,low threshold,fast response,and high modulation depth.The polarization function can also be realized by using ordered CNT film.A frequency-selective THz modulator is designed by using a combination of MXenes film and VO₂,which can control the transmitted light intensity of THz waves at different frequencies,and can also achieve a relatively high modulation depth under low VO₂ thickness.The research content is divided into the following parts:（1）Summarize THz wave and THz modulator,introduce the research status of THz modulator under different material systems,and explore the research status of THz modulator based on VO₂ and the problems that need to be broken through.（2）Using magnetron sputtering,VO₂ films are deposited on silicon dioxide（SiO₂）substrates,flexible CNT film substrates and flexible SN nanotube substrates.By studying the phase transition characteristics of VO₂ on different substrates,the influence of deposition parameters on the phase transition characteristics of VO₂ is analyzed.We can realized a flexible VO₂ film with good phase change characteristics.（3）Based on the combination of VO₂ and ordered CNT,an active adjustable THz modulator is designed,and the modulation bandwidth exceeds 2.3 THz.Due to the ultra-thin system characteristics of the CNT film,the excitation threshold of the THz modulator is very low,only 0.58 m W/mm~2,the response time is only 27 ms,and the modulation depth can exceed 90%.The ordered CNT enables the THz modulator to have a polarization function.These superior characteristics make VO₂-CNT THz modulator have potential application value in THz communication,THz imaging and other fields.（4）Based on the composite of MXene film and VO₂,a THz modulator with frequency selectivity is designed.Based on the EOT phenomenon,a femtosecond laser is used to cut rectangular array on the MXene film,and the self-supporting VO₂film is transferred to the rectangular array.Using the phase change characteristics of VO₂,amplitude modulation can be achieved at about 0.5 THz.Changing the size of the rectangular hole can change the position of the resonance frequency to achieve frequency selectivity.