Terahertz Functional Devices Based On Plasmon Resonance Effect

Terahertz(THz)waves possess the characteristics of low photon energy,abundant spectral resources,low time delay,and strong spectral resolution,which have enormous potential for applications in high-speed communication,imaging,biosensing,and other fields.However,functional devices that can drive the systematic application of THz technology are still in the initial stage of research.The scarcity of multifunctional,tunable,and miniaturized highperformance devices greatly limits the development of THz technology.Therefore,research and development of THz functional devices is a current research hotspot.Surface plasmon polaritons(SPPs)have been a hot topic of research after being proposed.In addition to overcoming the diffraction limit,SPPs provide the property of improving the transmission of devices,and near-field-enhancing property that enhances light-matter interactions.Utilizing the unique advantages of SPPs can significantly accelerate the development and application process of THz functional devices.Multiple THz functional devices based on the plasmon resonance effect are investigated in this paper,and the main work is as follows:1.A THz plasmon waveguide sensor based on high-quality factor(Q-value)Fano resonance is investigated by theoretical evaluation,mathematical modeling,and numerical validation.By introducing a metal wall into the waveguide coupled with a stub resonator,a sharp Fano resonance is excited by the destructive interference between the stub resonator and the metal wall.The Q-value is increased to 225,improving about 60 times.With the high sensitivity of the Fano resonance peak to the dielectric environment,the sensitivity of the sensor reaches 1.56 THz/RIU,and the figure of merit(FOM)is also increased to 195.The sensor offers the possibility of applying THz technology to biosensing applications.2.A dynamically tunable THz waveguide band-stop filter based on the plasmon-induced transparency(PIT)phenomenon is proposed,which is caused by the destructive interference between a stub resonator seen as the bright mode and a ring cavity regarded as the dark mode.The transmission spectrum changes from single-PIT to dual-PIT when the graphene is tuned.Thus,the THz filter has the characteristic of dynamically changing the number of stopbands.In addition,the performance of the filter can be further optimized by increasing the number of resonators.With good frequency tunability and large transmission modulation depth,the filter can be used as switches and modulators,and also has good prospects for application in THz high-speed communication field.3.A THz metamaterial near-perfect absorber with four independent functions has been realized,which is insensitive to polarization modes of incident light and still maintains acceptable absorption over a large range of incident angles from 0° to 60°.First,the selective perfect absorption of a single-frequency of THz waves is achieved.Second,perfect absorption of THz waves at multiple frequencies is achieved by simple adjustment of structure size.Third,the broadband absorption is achieved with an average absorption rate of over 99%from 1.2 to 2 THz.Finally,the combination of single-frequency and broadband absorption is achieved,which greatly expands the application prospects of the THz absorber.