Electromagnetic Induced Transparency Of Terahertz Metamaterial Based On Carbon Nanotube Films

Terahertz waves(THz)have broad development prospects in medical,biological,communication,safety checks,disease diagnosis,and other fields because its high signal-to-noise ratio,high penetration,and low photon energy characteristics.However,due to the poor response of most substances in nature to electromagnetic waves in the THz frequency band,and the shortcomings of existing THz devices such as large volume and weight,the promotion and development of THz technology are limited.The recent rise of THz metasurfaces has brought new opportunities to effectively control the transmission performance of THz waves in media.Meanwhile,carbon nanotubes(CNTs)have become a hot research field due to its excellent THz band light absorption and modifiable properties.The electromagnetic induced transparency(EIT)phenomenon has strong dispersion characteristics,and its rigorous experimental conditions limit its development and application,the emergence of metasurfaces solves this problem.Due to the diversity and flexibility of metasurfaces design,exploring the EIT phenomenon of THz metasurfaces using CNTs as materials on the basis of existing THz metasurfaces is of great significance for promoting the theoretical research,practical applications,and development of new THz functional devices.In this paper,the EIT-like of THz metamaterials based on CNTs films was designed and simulated to generate reflective EIT-like phenomenon,and the mechanism of electromagnetic induced transparency was analyzed from both theoretical and electric field perspectives.Then,a THz metasurface based on CNTs was designed that can generate clear mode transmission EIT.The generation mechanism was analyzed,and the designed device was studied using analytes of different thicknesses and refractive indices.The sensitivity of the metasurface was 320 GHz/RIU,and the sensitivity about the amplitude shift was also obtained,which was about 13.04%/RIU.Finally,a dual-mode EIT terahertz metasurface based on CNTs films was proposed.Under the excitation of THz waves,this metasurface can generate two different modes of EIT windows.The mechanism of their generation is analyzed.The first mode is derived from surface plasmon resonance,and the second mode is derived from the resonance of periods in CNTs films.In the case of incident waves at different angles,the transparent window positions of both modes with phase transitions and dispersion.At the same time,the EIT slow light characteristics of three types of metasurfaces were verified.Through calculation,the peak group delay of the reflection window was 1.13 ps,and the peak group delay of the transparent window was 2.12 ps.When the dual mode transmission metasurface under the vertically incident THz waves,the group delay of the first mode is 16.77 ps,and the group delay of the second mode is 14.61 ps.