Research Of The Phenomenon Of Electromagnetically Induced Transparency-like Of Terahertz Metamaterial

Due to the unique electromagnetic advantages that natural materials and chemical synthetic materials do not have,artificially manufactured metamaterials have attracted widespread attention from researchers in recent years.The electromagnetic-like transparency effect of terahertz metamaterials can obtain a narrow-band transparent window in a broadband absorption background and cause strong dispersion in a narrow spectral range,which significantly slows down the group velocity of the propagating terahertz pulse,so it is very suitable for preparing refractive index sensors,optical switches,optical modulators,optical filters,and slow-light devices.In this paper,three terahertz metamaterials with different structures are designed to achieve electromagnetic-like transparency,and the mechanism of the three structures is analyzed.The tunability of the transparent window of metamaterials is discussed through two methods: passive modulation and active modulation.Finally,the sensing performance of transparent windows of several metamaterials is studied.The specific research content of this article can be divided into the following aspects:(1)Design a unilateral symmetrical metamaterial structure based on a cut-wire resonator and a U-shaped split-ring resonator to achieve electromagnetic-like transparency and analyze the coupling mechanism between bright and dark modes.By changing the structural parameters of metamaterials to passively modulate the transparent window,the parameter modulation range of the transparent window is obtained.By embedding photosensitive Si at different positions of metamaterials,the influence of the applied light field on the transparent window under active modulation and the corresponding modulation range were analyzed.(2)Based on the symmetric structure,the lateral distance between the split ring and the cut-wire resonator is changed to obtain a unilateral asymmetric structure metamaterial that can realize the EIT-like phenomenon,and the transmission mechanism of the structure is analyzed.From the perspective of passive and active modulation,the parameter variation range of the metamaterial transparent window is also determined.Compared with the modulation effect of the symmetric structure,the asymmetric structure can achieve small parameter changes and produce a greater modulation effect.Finally,the refractive index sensing performance of cutwire resonator metamaterials,unilateral symmetrical structure metamaterials and asymmetrical structure metamaterials were studied and compared respectively.It was found that the first two metamaterial structures can achieve 63.6 GHz/RIU and 84.4 GHz respectively /RIU sensitivity response,asymmetric structure metamaterials have achieved a refractive index sensitivity response of up to 102.3 GHz/RIU.(3)A bilateral asymmetric metamaterial structure that can realize EIT-like double transparent windows in the terahertz frequency band is proposed,and the coupling mechanism of the double transparent windows is simulated and analyzed.Through the passive and active methods to study the tunable performance of the dual-band transparent window,it is found that passive modulation can achieve independent modulation of any window in the double transparent window,and the active modulation method can not only ensure independent modulation of any window,but also The narrowband/broadband transparent window can be modulated.In addition,the refractive index sensing characteristics of this metamaterial structure were explored,and the research results found that the structure can also achieve up to 96.7 GHz/RIU refractive index sensitivity.