Study On The Characteristics And Sensing Performances Of The Plasmons In THz Domain

Terahertz band has received much attention and has been researched intensively because of its unique spectrum characters.Among all the studies about terahertz band,terahertz plasmon are widely designed as refractive index sensors as it's sensitive to the refractive index of the surrounding material.The studies about terahertz metamaterial shows that the electromagnetically induced transparency(EIT)-like phenomenon in terahertz domain is the result of coupling of terahertz plasmon.Hence,the plasmon based on EIT-like phenomenon is EIT-like metamaterial.Moreover,the high dispersion property of the EIT-like phenomenon makes the EIT-like metamaterial more sensitive to the surrounding's refractive index.Therefore,in recent years,the EIT-like metamaterial in terahertz domain has been a hot spot in sensing field.In this paper,the characteristics and parameters of the metal in terahertz domain is studies.The theory and designs of EIT-like metamaterials are discussed in detail.The main works of this paper are listed as follows:(1)A terahertz metamaterial based on magnetic trapped resonance is designed.The structure consists two asymmetric metal strips.By exciting the magnetic resonance mode in this structure,a narrow band EIT-like transparent window with high Q value is observed.The sensing performance of the structure is simulated and analyzed.(2)A terahertz metamaterial composed by two pairs of asymmetric metal strips is designed.By breaking the symmetry of the structure,the magnetic resonance mode is created,and the EIT-like transparent window emerges.The influence of structural parameters on the Q value of the EIT transparent window and the sensing performance of the structure are discussed.The sensing performance is better than that of the structure consists of two asymmetric metal strips.The proposed structure can achieve higher Q value and better sensing performance by simply adjusting the parameters of the strips.The metamaterial offers a new idea for designing EIT-like metamaterial based on trapped magnetic resonance.(3)Designed a bright-bright mode coupling and a bright-dark mode coupling metamaterial.These two metamaterials are all composed by one metal strip and two identical split ring resonators(SRRs).The principle of these EIT-like phenomenon occur in these two structures are analyzed.The sensing performance of the two structures are simulated.Analyzing the differences between the two structures,the bright-bright coupling mode structure has a better sensing performances.The structure based on bright-bright coupling was fabricated,while the transmission characteristics were measured by terahertz femtosecond(THz-TDS)system which is in good agreement with the simulations.(4)A tunable EIT-like metamaterial is proposed.The Q value of the EIT transparent window can be adjusted by the rotation of the metal strip.The Q value is much higher than the structures mentioned in other papers.The sensing performance of the structure is simulated and analyzed.