The Research On The Refractive Index Sensor Of Terahertz Metamaterial Structure

Terahertz(THz)radiation generally refers to electromagnetic radiation whose frequency ranges from 0.1 to 10 THz between microwave and infrared bands.Terahertz technology has potential applications in communications,imaging,detection,and medical fields,of which terahertz refractive index sensor is an important terahertz device for sensing and detection.Metamaterials are artificially designed periodic structure materials and has unique properties that other materials do not possess.It can be applied in terahertz refractive index sensors to achieve high sensitivity and label-free detection.The research of terahertz metamaterial refractive index sensor has important theoretical value and practical significance.Firstly,the electromagnetic properties and the basic principle of electromagnetic induced transparency(EIT)effect of metamaterials are analyzed.The theory of refractive index sensing of metamaterials is analyzed by the electric field response,magnetic field response and the theory of coupling model of EIT effect of metamaterials.Secondly,based on the EIT-like effect,three kinds of terahertz refractive index sensors with metamaterial structure are designed by CST MWS 2015,and the influence of their main geometric parameters on the sensing performance is discussed.The first one is an asymmetric metamaterials refractive index sensor consisting of four open resonant rings and metal strips.Its Q value is 92.0,the refractive index sensitivity is 61.0 GHz/RIU(Refractive Index Unit),and the FOM(Figure of merit)value is 8.5.The second one is based on the asymmetric structure and the principle of Babinet complementarity,which combines the asymmetry and complementarity,and a complementary metamaterials refractive index sensor composed of metal bars is designed.The sensor makes the substance to be measured more fully contact with the sensing part,thus improving the refractive index sensitivity.Its Q value is 104.5,the refractive index sensitivity is 73.5 GHz/RIU,and the FOM value is 6.3.The third one is to design a combined metamaterials refractive index sensor which is composed of a circular resonant ring and a square resonant ring by constructing two resonant elements with nearly the same resonant point.The Q value is 63.0,the refractive index sensitivity is 96.2 GHz/RIU,and the FOM value is 7.8.The performance of this sensor is better than the former two,and its structure is simple and easy to process.Finally,the combined metamaterial refractive index sensor is fabricated and tested,and the experimental results and simulation results are compared and analyzed.In summary,the terahertz metamaterial structure refractive index sensor designed in this paper has good refractive index sensing performance and has important potential application value in terahertz detection technology.