Research On Terahertz Metamaterial Absorbers Based On Micro 3D Printing Technique

Terahertz waves have unique properties such as high penetration,high bandwidth,and low photon energy,which make them embody great potential in the fields of electromagnetic imaging,high-speed communication,and biomedical detection.Terahertz metamaterials,as a device that can effectively control terahertz waves,have attracted extensive attention in the scientific research community.Since the feature size of the unit structure of metamaterials is limited to the subwavelength scale,the structural units constituent of terahertz metamaterial devices is generally in the order of micrometers.Therefore,the processing of terahertz metamaterials mainly relies on the traditional micro-nano manufacturing process,which includes cumbersome procedures,long time-consuming and high costs.Based on the micro-stereolithography 3D printing technology and resin metallization process,this thesis conducts a detailed study on the new fabrication process of terahertz metamaterials,and different fabrication methods are formulated for different structural types of metamaterials.Firstly,a manufacturing process was developed for all-metal terahertz metamaterials.The metamaterial resin structure was fabricated by micro-stereolithography 3D printing technology,and then a continuous metal coating layer was deposited on the surface of the printed resin structure by magnetron sputtering deposition coating process.A vertical split-ring resonator-based terahertz absorber was designed and fabricated by the developed process.The THz-TDS test shows that the fabricated sample achieves 96% absorption at 0.8THz,which was consistent with the numerical simulation and verified the effectiveness of the proposed process.The high-Q factor resonance of the metamaterial absorber can be potentially applied in the field of substance sensing,and its sensing capability is verified by the sensing performance of the lactose and galactose powders.Secondly,based on the micro channel liquid metal filling process,another fabrication method of all-metal terahertz metamaterials is developed.The resin model of microchannel was first printed by micro-stereolithography 3D printing technology,and then liquid metal was filled into the microfluidic channel by atmospheric pressure.The cross VSRRs-based terahertz metamaterial was designed and processed by the developed manufacturing process.The simulation results and experimental measurements show that the prepared samples have three high-intensity resonance peaks in the terahertz band,which confirms the effectiveness of the established protocol.Thirdly,the fabrication process of independently patterned terahertz metamaterials is studied,and the metamaterials are fabricated by combining the micro-lithography 3D printing and the highly directional metal coating deposition process.The samples fabricated by the new process have the characteristic that the resonant units are out of the plane.Firstly,a typical cross-shaped metamaterial absorber was taken into account as the prototype to demonstrate the effectiveness of the proposed technique.Secondly,a broadband and a triple-band MA were realized by combining four cross-shaped resonators and the alternative of the cross-shaped resonator.Both experimental measurements and theoretical simulation exhibit the absorption performance of three types of 3D printed MA samples.Three fabricated devices verified the universality of the proposed fabrication method in different scenarios.Finally,the electromagnetically induced transparency effect in the terahertz frequency band is investigated according to the proposed fabrication process of independent patterned metamaterials.Based on the bright-dark coupling mode,a three-dimensional reflective terahertz electromagnetically induced transparency device is designed.When the symmetry of the device is broken by the offset of the bright mode structure,the coupling channel between the bright and dark modes is established,and a transparent window will appear in the reflection spectrum of the device at the original opaque frequency position.With the advantage of the three-dimensional structure,the resulting transparent window can be regulated by adjusting the lateral displacement and the height of the bright and dark modes.Two samples with the smallest and largest lateral displacement were fabricated and the electromagnetically induced transparency effect of the designed device is verified by experimental measurements.