| Terahertz(THz)radiation exhibits many unique properties,and has gradually developed into a hot spot for basic and applied research in cross-disciplinary.The enhancement and manipulation of the strong coupling interaction between THz waves and matter to form high quality factor(Q-factor)resonance with localized electromagnetic field is of great significance for many practical applications including THz ultrasensitive sensing,imaging,narrow-band filters and low-threshold lasers.However,due to the long wavelength of THz waves,it is difficult to interact fully with natural matter.Achieving strong interaction between terahertz waves and matter to produce low-loss high-Q resonance has been one of the urgent technical difficulties to be solved.Metasurfaces are artificial arrays of subwavelength structures that can flexibly modulate the polarization,amplitude,and phase information of electromagnetic waves,providing a new method for manipulating the interaction of terahertz waves with matter.Therefore,in this thesis,the THz high Q-factor electromagnetic resonance is studied and discussed on the basis of metasurface,using the strong coherent coupling between single-mode,dual-mode and multi-mode of resonance,which is as follows:1.Research on THz high-Q guided-mode resonance with dielectric grating structure.In order to solve the problem of high loss of THz perfect absorption resonance,a subwavelength dielectric grating slit waveguide is designed to realize THz dual-band high-Q perfect absorption resonance by integrating a Fabry-Perot cavity and a gold reflective film into the dielectric grating,and the coupled-mode theoretical analysis of high-Q perfect absorption characteristics is carried out.Then,the effects of grating period,grating width and grating depth of the dielectric grating slit waveguide on the transmission characterist ics of dual-band high-Q perfect absorption resonance are investigated,and the sensing performance capability of dual-band high-Q perfect absorption is discussed and analyzed.2.Research on THz high-Q Fano recontructive coherent electroresonance of metallic split ring arrays.Theoretical study of the THz spectral properties of the single metallic rod array was carried out.A THz high-Q metasurface consisting of an array of biased practically processed metallic rings was designed to induce excitation of the THz high-Q recontructive coherent mode.The transmission properties of the THz high-Q recontructive coherent mode are investigated,and the physical mechanism of the THz high-Q recontructive coherent Fano mode is analyzed.Subsequently,the geometric effect of the metallic ring and the refractive index of the substrate on the coherent mode properties of the THz high-Q recontructive coherent mode are studied and discussed.3.Research on THz Fano coherent magnetic resonance of metallic split ring arrays.In order to solve the problem of large losses in THz magnetic resonance,transmission spectra of free-standing metallic split-ring intrinsic modes are investigated,and transmission spectra of terahertz high-Q Fano magnetic resonance in the presence of a substrate are further investigated.The transmission properties of THz high-Q magnetic resonance and fundamental-order magnetic dipole modes dominated by magnetic dipole moments in multipole induction are studied and analyzed,experimental measurements are completed,and comparative analysis of simulation results and experimental results is performed.4.Research on bound-states in the continuum of metalliclic meander-like grooves waveguides structures.Spoof surface plasmon polaritons have the advantages of low loss,field binding and low radiation compared to spps supported by metallic surfaces.A metalliclic meander-like grooves waveguides structures is designed,dispersion analysis of the spoof spps is performed,and the electromagnetic scattering cross section of the metallic meander-like grooves waveguides structures at finite length is studied and analyzed.Then,the bound-states in the continuum characteristics of the spoof surface plasmon polaritons based on coupling coherence are further investigated when the grooves are filled with high-refractive index dielectric,and the mode transformation of the metallic meander-like grooves waveguide structure is analyzed when the aspect ratio changes. |
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