Research On Tunable Electromagnetically Induced Transparency In Terahertz Frequency Band Based On Metamaterials

In the three-level atomic energy system,the electromagnetically induced transparency(EIT)effect is a quantum destructive interference phenomenon.A narrow band transparent window appears in the broadband absorption spectrum when the frequency of the probing beam coincides with the frequency of the atomic transition.This phenomenon is caused by quantum cancelling interference between the excitation channels of optical atoms.The necessity for ultra-stable lasers,an experimental setting with extremely low temperatures,and a gaseous atomic environment are just a few of the challenges that must be overcome in order to realize electromagnetically induced transparency in atomic systems.Metamaterials(MTMs)are a class of periodic unit structures that have been created artificially.They exhibit electromagnetic properties that are not present in natural materials and have the ability to control the transmission properties of electromagnetic waves.The realization of EIT-like based on metamaterials is an extension of electromagnetically induced transparency.Artificial cell structures allow for the realization of electromagnetically induced transparency at room temperature without being constrained by difficult experimental conditions,considerably advancing the study and practical use of electromagnetic induced transparency.Strong dispersion will cause "slow light" and nonlinear effects on the electromagnetically produced transparent transmission window.Because to these qualities,it is frequently employed in devices such as slow light devices,optical memory,nonlinear switches,and others.In this paper,we mainly focus on the realization of tunable electromagnetically induced transparency(EIT)in terahertz band by using metamaterials,and achieve amplitude adjustable EIT and frequency adjustable EIT.The main contents are as follows:1、Two kinds of electromagnetically induced transparent metamaterials with active amplitude tunable in the terahertz band were designed.By changing the light intensity,the conductivity of the embedded semiconductor Ga As changes,and the amplitude of electromagnetically induced transparency is optically controlled.The mechanism of electromagnetically induced transparency is studied by analyzing the surface current.The impact of changes in the two resonators on the transmission curve is discussed,and the group delay established through simulation and calculation supports the structure’s optical control adjustment to the slow light effect.In addition,on the basis of the proposed unimodal electromagnetically induced transparency metamaterial,the open-ring resonator can be added to realize the optically controlled adjustment of the amplitude and group delay of the bimodal EIT-like.2、An active frequency tunable electromagnetically induced transparent metamaterial in the terahertz band was designed.By changing the external voltage of the solid state plasma,the metamaterial can switch freely in two states.The generated electromagnetic induced transparency like can realize the switching of the transmission window within a certain range,which realizes the active tuning EIT-like in the terahertz frequency range.The mechanism of electromagnetically induced transparency is analyzed by studying the electric field distribution;The influence of the distance,size and incident wave angle between the two resonators on the transmission curve is discussed;The adjustment of the structure to slow light effect is verified by the group delay obtained by calculation and simulation.Finally,the Lorentz model is used to fit the transmission curve,which shows that the linearly coupled Lorentz oscillator model can be used to study the proposed electromagnetically induced transparency.