The Research Of Narrow Band Terahertz Absorber Based On Metamaterials

With the emergence of various high-performance terahertz sources and terahertz detectors,terahertz functional devices have become a research hotspot in the field of terahertz science and technology.The terahertz narrow band absorber studied and designed in this dissertation is an important terahertz functional device,which has the characteristics of near-perfect narrow band absorption of terahertz waves.It has broad application prospects in the fields of biological sensing,narrow band thermal radiation and photoelectric detection.Firstly,the research background and research status at home and abroad of terahertz absorber are analyzed in this dissertation.The negative permittivity and negative permeability characteristics of metamaterials are analyzed,and the perfect absorption method of terahertz wave based on impedance matching theory,magnetic resonance theory,and interference theory is studied.Then,the narrow band absorption performance of three metamaterial structures,namely square ring,circular ring,and strip structure,is compared.The square ring structure with better performance is selected as the basic structure of the terahertz narrow band absorber,and the first terahertz narrow band absorber is designed.It can absorb 99.353% of the incident terahertz wave at 0.374 THz,and the full width at half maximum relative to the absorption frequency is 0.756%.The absorption mechanism of the absorber is studied by analyzing the distribution of electric field,current and magnetic field at the absorption frequency.Then,based on the square ring structure,the second and third terahertz narrow band absorbers are designed,and their unit structures are split ring and windmill structure,respectively.Compared with the first square-ring structure absorber,the second split ring structure absorber has better narrow band absorption performance,which can achieve99.842% absorption of incident terahertz wave at 0.402 THz,and the full width at half maximum relative to the absorption frequency is 0.494%.Compared with the first two types of absorbers,the third type of windmill structure absorber has dual-band narrow band absorption characteristics.It can absorb 99.825% and 99.159% of the incident electromagnetic wave at 0.371 THz and 0.464 THz,and the full width at half maximum relative to the absorption frequency is 0.763% and 0.307%,respectively.Besides,on the one hand,the decoupling model of the split ring structure absorber is established by using the interference theory,and the absorption mechanism at the absorption frequency is studied.On the other hand,the absorption mechanism of the windmill shape structure absorber at two absorption frequencies is studied by using the magnetic resonance theory and the interference theory,respectively.Finally,the split ring and windmill structure absorbers with good absorption performance are processed and tested.The test results and simulation results of the absorber are compared and analyzed with high consistency.In summary,the terahertz narrow band absorber designed in this dissertation has good narrow band absorption performance.It has important potential application value in the field of terahertz sensing and detection.