Research On Novel Kinds Of Terahertz Wave Switch

Along with an in-depth investigation on terahertz radiation source and detection technology,terahertz technology has been gradually introduced to the practical applications.Therefore,it has an increasing demands for the terahertz functional devices which can take control of terahertz wave in a directly way such as the area of switch.The terahertz wave switch has imposed a significant role in composing numerous THz systems.As a result,this paper attempts to propose the Kretschmannn and Otto prism model to excite the terahertz surface plasmon resonance,as well as control the transmission of terahertz wave.In addition,it also designs four novel terahertz wave switches,whose feasibility is confirmed based on theoretical analysis and simulation calculation.The main research contents are concluded as follows:1.With the application of the Kretschmann prism coupling configuration and periodic structure,electronically controlled terahertz wave switch is put forward in this work.The switch consisted of prism-liquid crystal-metal.Besides,the proposed metal film is penetrated through using a linear array of subwavelength rectangular grooves and silicon is also filled into the grooves.The terahertz wave is incident from the left side of the prism at a fixed angle and a terahertz wave detector is installed on the prism external position of the reflected terahertz wave beam.Besides,the refractive index of the liquid crystal can be altered through making the adjustment of the external electric field.As a result,the wave vector matching is influenced.Therefore,the reflectance is controlled in a dynamical way.The incident terahertz wave frequency is 1THz,and the incident angle is 35.05°.On the condition that there is no external electric field,the reflectivity is 0.07%.At this moment,the switch is in the“OFF”state.When there exists an applied electric field,the reflectivity can even reach 98.53%.Therefore,the prism structure occurs total reflection,so that we could make a definition of the terahertz wave switch as the“ON”state.In addition,the calculation of extinction ratio is 31.48dB of the designed switch.2.According to the Kretschmann prism coupling configuration and two graphene layers structure,this paper attempts to introduce the electronically controlledterahertzwaveswitch.Thecomponentoftheswitchis prism-graphene-SiO₂-graphene-InSb.The terahertz wave is incident from the left side of the prism at a fixed angle and a terahertz wave detector is the installation of the prism external position of the reflected terahertz wave beam.Graphene offers great chances to dynamically administrate the terahertz wave based on the application of the external electrical field.In addition,the incident terahertz wave frequency is 1THz with the incident angle as 35.42°.Without the observation of the external electric field,the reflectivity is 2.63%.Then,the switch is in the“OFF”state.Based on an applied electric field,the reflectivity can get to 93.01%.Consequently,the prism structure occurs total reflection.Besides,the terahertz wave switch can be defined as the“ON”state.Apart from that,the calculation of extinction ratio is15.49dB of the designed switch.3.On the basis of the Otto prism coupling configuration and metal surface structured with periodic V-grooves,temperature control terahertz wave switch is proposed.The surface of the metal layer is corrugated with periodic V-shaped grooves,and the groove is full of VO₂.Also,the terahertz wave is incident from the left side of prism at a fixed angle and a terahertz wave detector is set on the prism external position of the reflected terahertz wave beam.Along with the changes of the temperature,the dielectric constant of the VO₂ will change accordingly,influencing the reflectivity of terahertz wave.The incident terahertz wave frequency is 1THz,and the incidence angle is 39.56°.Once the ambient temperature is 55℃,structure produces surface plasmon resonance and the reflective terahertz wave is nearly0.96%.As a result,the switch is in the“OFF”state.As the ambient temperature is75℃,the reflective terahertz wave is almost 99.97%.As a consequence,we define the terahertz wave switch as the“ON”state and the calculation of extinction ratio is20.18dB of the designed switch.4.Based on the Otto prism coupling configuration and monolayer graphene structure,electro-optical double controlled terahertz wave switch is involved in this work.Theswitchcontrolsreflectionintensityfromthe prism-air-graphene-SiO₂-polymer interface by means of external voltage bias or pump laser.The terahertz wave is incident from the left side of the prism at a fixed angle and a terahertz wave detector is installed on the prism external position of the reflected terahertz wave beam.The combination of voltage regulation and laser regulation make the device be possessed with both the good control ability and flexibility.Besides,the incident terahertz wave frequency is 1THz,and the incident angle is 54.31°.With no external electric field and pump laser,the reflectivity is0.04%.Then,the switch is in the“OFF”state.When an external applied voltage alters the chemical potential of graphene（μ_c=0.2eV）,the reflectivity can obtain95.89%.Thus,the prism structure appears total reflection,and we can identify the terahertz wave switch as the“ON”state and the calculation of extinction ratio is33.8dB of the designed switch.Altering the refractive index of the polymer layer based on the external pump laser power excitation,the reflectivity can even get to98.90%.Therefore,total reflection can be observed in the prism structure.In addition,the terahertz wave switch can be defined as the“ON”state and the extinction ratio of the terahertz wave switch is 33.9dB.