Study Of Terahertz Wave Modulator Based On Vanadium Dioxide

Terahertz?THz?wave has attracted extensive attention in recent years with its potential application for wireless communications,military inspection and other areas due to its outgoing properties such as strong penetration and high resolution,etc.Therefore,functional devices of THz wave are indispensable for the development of terahertz science and technology.Metamaterial as an artificial structure can represent unprecedented characteristics in THz region is used widely in THz functional devices,as well as its responses mainly depend on the structural design of the subwavelength unit cells.Vanadium dioxide?VO₂?is a chromogenic metallic oxide that can achieve reversible transition from insulator to metallic phase as fast as femtosecond level,which makes it be a promising candidate for the dynamic control of THz waves.Moreover,its phase transition could trigger by many factors such as temperature,voltage,optical pump,etc.Based on those theories and technology,in this thesis,the introduction of terahertz technology and relative devices is briefed,especially the tunable devices based on vanadium dioxide thin film.And then the high performance VO₂ thin film was deposited by different technology.Finally,two types of THz wave modulators based on the VO₂ thin film cooperated with different metasurface configuration are designed and fabricated.Those results are as follows:1)The VO₂ thin film was deposited on single crystal intrinsic silicon substrate via different DC reactive magnetron sputtering method,and Ar/O plasma irradiation was proposed for post-treatment of some VO₂ films.The result shows that VO₂ thin film deposited by pulsed DC reactive magnetron sputtering method performed best performance.With the deposition time adding,the film has better crystallization ability.VO₂ thin film deposited four hours performed pure monoclinic phase with conspicuous phase transition ability?40%optical modulation?and high infrared modulability?24.12%?.2)Based on this VO₂ thin film,a CI type of thermally tunable terahertz wave modulator was proposed with 40%inhibit depth on 0.47THz wave around 0.2THz bandwidth at the“on”state,and full reflection on 0.1-2THz wave at“off”?after VO₂ transition?state.The simulation result shows that the C-ring serve as the dipole which coupled with electromagnetic wave to excite the resonant peak and the terahertz wave mainly concentrates on the inner and outer edges of the C-ring for transmission.The decrease of resonance peak intensity and blue shift of position was observed with the period size increase.3)A WHEEL type of thermally tunable terahertz wave modulator was proposed with 70%inhibit depth on 0.4THz wave around 0.11THz bandwidth at the“on”state,and full reflection on 0.1-2THz wave at“off”?after VO₂ transition?state.The simulation result shows that the four split ring of each unit cell can serve as independent dipoles which coupled with electromagnetic wave to excite the resonant peak respectively,and the terahertz wave mainly concentrates on the up and below ring of O-split ring for transmission.It can be observed that the full width of half maxima of resonance peak increased and peak position occurred blue shift with the line width increase.