Terahertz Wave Transmission And Manipulation Technology Based On Spoof Electromagnetic Metasurfaces

Terahertz waves have significant value in various applications such as communication,security,and astronomical observation.One of the key challenges in terahertz technology is the transmission and manipulation of terahertz waves.The wavelength of terahertz waves typically falls within the micron to millimeter range,which limits conventional structures due to wavelength matching issues and size restrictions.Consequently,meeting the demands of emerging terahertz circuits and devices becomes challenging.Moreover,conventional materials exhibit weak responses in the terahertz frequency range,which restricts the ability to control terahertz waves effectively.To address these limitations,spoof electromagnetic metasurfaces have emerged as a promising solution.These metasurfaces consist of periodic or aperiodic arranged spoof unit structures of sub-wavelength size on a two-dimensional plane or surface.They can stimulate unique physical phenomena that cannot be or are difficult to achieve in natural media and conventional materials.As a result,they offer new avenues and possibilities for practical applications in terahertz technology.Different types of spoof electromagnetic metasurfaces have different specific applications.Among them,spoof surface plasmon polaritons（SSPPs）provide a means to achieve the transmission and guided-wave properties of spoof electromagnetic metasurfaces.They guide terahertz waves to propagate on the metasurfaces,enabling the creation of desired constraint properties.Furthermore,SSPPs offer compactness,integrability,and low crosstalk,enabling the development of smaller,higher-performance,and more steady terahertz solid-state devices.Additionally,the terahertz perfect absorber represents a specific application of spoof electromagnetic metasurfaces in the realm of wave control characteristics.It utilizes the micro-nano structure of spoof electromagnetic metasurfaces to regulate the reflection,transmission,and scattering of incident waves on the surface of the absorber,achieving absorption or modulation of the terahertz waves.Building upon the investigation of terahertz wave transmission and manipulation characteristics facilitated by spoof electromagnetic metasurfaces,this dissertation explores the application of terahertz transmission lines,filters,waveguide power based on SSPPs,as well as the design and analysis of terahertz absorbers and adjustable devices using spoof electromagnetic metasurfaces.This work lay the foundation for the application of spoof electromagnetic metasurfaces in the terahertz frequency band.The main research contents are presented as follows:1.Terahertz wave transmission technology based on spoof surface plasmon polaritons（SSPPs）.Based on the achievement of miniaturized terahertz SSPPs transmission line structures,this dissertation introduces the innovative concept of on-chip antenna transition for the mode conversion between rectangular waveguide and SSPPs for the first time.The transition structure,utilizing dipole antennas,significantly reduces the space required by the conventional mode conversion techniques.It also avoids difficulties in processing and assembly within the terahertz band.Moreover,the proposed structure exhibits remarkable conversion efficiency over 80%within the frequency range of 195-250 GHz.Consequently,it offers a more convenient and effective method for practically applying SSPPs transmission line in terahertz modules and systems.Additionally,two miniaturized on-chip SSPPs transmission lines are developed to apply in terahertz monolithic integrated circuits,and their low crosstalk characteristics are verified.2.Terahertz filtering technology based on SSPPs.A novel terahertz wideband-bandstop filter structure,comprising a combination of split resonant ring（SRR）and complementary split resonant ring（CSRR）,is proposed in this dissertation.The structure achieves an expanded suppression bandwidth（from 10.7%to 21%）and improved suppression depth within a compact cabling environment by simultaneously incorporating SRR and etching CSRR.This flexible pass-stop-pass-stop characteristic holds significant importance for the development of terahertz filters.Furthermore,thanks to the inherent low-pass characteristics of SSPPs,the properties of SSPPs in bandpass filtering and tunable filtering are further investigated,thereby establishing a solid foundation for the utilization of SSPPs filtering technology in terahertz functional devices.3.Terahertz power combiner technology based on SSPPs.A composite terahertz SSPPs planar structure exhibiting absorption characteristics is proposed based on the electromagnetic loss properties of nickel（Ni）and the low-pass characteristics of SSPPs.This pioneering approach of composite Ni-SSPPs is introduced into the terahertz power combiner technology.The composite structure enables the realization of a high isolation terahertz T-junction power divider（about 18 d B）and a high-power capacity waveguide directional coupler.This innovative power divider technology eliminates the need for conventional wedge-shaped or cone-shaped loss-absorbing materials and thin film resistors.Moreover,it overcomes the power capacity limitations associated with the highest operating temperatures of such materials.By integrating the proposed method with TMICs chip,comprehensive testing is conducted on a 220 GHz power combiner module（combing efficiency of 87%）,a 220 GHz frequency doubling combiner module（output power of 48 m W）,and a 3mm frequency band directional coupling combiner module.The introduced composite Ni-SSPPs approach presents a promising design concept for the future development of high-power terahertz solid-state sources,offering new possibilities in this field.4.Terahertz metasurface narrow-band absorber design.Based on the working principle of the metasurface perfect absorber（MPA）,a novel absorber design using an“inverted-cross-star”structure is proposed.This absorber utilizes its distinctive charge localization enhancement properties to achieve remarkable attributes such as a high Q value（up to 69.8）,an ultra-thin thickness（onlyλ₀/188）,and excellent angular insensitivity.This high-Q narrowband absorber exhibits remarkable sensitivity and linearity in refractive index sensing of materials such as large molecule films and solutions.Furthermore,a dual-band terahertz absorber is designed,and two different refractive index materials,PDMS and PI thin films,are adhered to the surface of the terahertz absorber.The experiment successfully validates the efficacy of the MPA in refractive index sensing,thereby establishing a solid groundwork for the future practical application of terahertz metasurface devices.5.The design of terahertz adjustable metasurface device.Drawing upon the principles of metasurface absorption and the emerging tunable materials,this dissertation introduces novel terahertz multifunctional tunable metasurfaces that incorporate both graphene and vanadium dioxide materials.These metasurfaces exhibit dual functions of broadband multifrequency absorption or absorption transmission switching It can achieve dual regulation of scattering parameters such as absorption and transmittance of functional devices by independently changing the Fermi level of graphene or the conductivity of vanadium dioxide.o experimentally validate these tunable attributes,we conduct comprehensive testing on the vanadium dioxide-based metasurface absorber.This systematic exploration paves the way for the development of intelligent terahertz metasurface systems in the foreseeable future.