Studies On Design And Properties Of Metamaterials Analogue Of Electromagnetically Induced Transparency

Electromagnetically induced transparency(EIT)effect arises from the quantum interference in atomic systems,which has the transmission characteristics of low loss,narrow band,high transmittance and strong dispersion with the electromagnetic wave through the medium.Analogues of EIT effects in metamaterials,not only have the same electromagnetic properties as EIT atomic systems,but also benefit from the randomicity and intentionality of electromagnetic metamaterial construction,and not be subject to the harsh experimental conditions,such as low temperature and high intensity laser etc.Therefore,more and more attentions have been paid to EIT effects and its electromagnetic applications.Analogues of EIT effect in metamaterials are of great realistic significance and broad application prospects in slow light technology,optical storage,high sensitivity sensing,frequency selective surface and other related fields.In this paper,we summarized the related research achievements of EIT metamaterials firstly,and then used mechanical oscillator stystem analog to the atomic system,analyzed the energy absorption and dispersion properties of single harmonic oscillator,bright-dark double harmonic oscillators and bright-dark-dark three resonators mechanical coupling systems.From the results,we got the formation mechanism and the key influence factors of EIT effects as also dispersion characteristics,such as damping coefficient,coupling strength,intrimsic oscillation frequency etc.Using the mechanical oscillator coupling mode as the theoretical basis,we constructed four different microwave and THz EIT metamaterials,analyzed the electromagnetic mechanism and studied the electromagnetic characteristics through numerical simulation and experimental measurement,and then developed their applications as microwave switch,refractive index sensor.Results in this thesis can be summarized as follows:Firstly,the manipulation of EIT effects in microwave-band was studied.In Chapter 3 and 4,we constructed two kinds of microwave EIT metamaterials,respectively realized the switch of EIT transparency window and tailoring it from single to dual-bands.The elecrtromagnetic mechanism of tunable EIT response were analyzed by dipoles interference theory and harmonic oscillators coupling model.The switchable EIT effect can be realized by the structure rotation and polarization of the incident electric field,and has potential application for the microwave switch and tunable microwave devices due to its narrow-band and high-transmittance characteristics.And the tailoring of dual-band EIT transparency window is achieved through structural parameters tuning,and the proposed structures show good slow light effects,the group index of single band EIT transmission window reaches 130,for dual-band,120 and 150 respectively.Secondly,the construction of broad-band and polarization-independent EIT metamaterials have been studied.Trough the extension of harmonic oscillators coupling model,we got the result that a broad-band transparency EIT effect can be realized when the system have large detuning factors with the eigen-frequencies and strong oscillator coupling strength.Then,we proposed a C4 rotational symmetric structure from two orthogonal double-end fork(DEF)metal structures,and the numerical and experimental studies showed that the bandwidth of its polarization-insensitive EIT transparency window can be up to 3.63 GHz by the interference of magnetic resonance induced by electrical resonance.The research results provide a reference for the construction of microwave broad-band and polarization-independent EIT metamaterials.Finally,a terahertz EIT resonance with high Q and high transmittance was adopted for refractive index sensing.It was constructed by metal cut wires,and the high Q EIT transparency peak was formed by the the weak radiation of the electric quadrupole excited by the strong radiation of the electric dipole.The studies of sensing properties show that when the EIT metamaterial was covered by 3 ?m-thickness analyte,the sensitivity can reach 0.2695 THz/RIU and the FOM is about 5.44.Moreover,the sensitivity is inversely proportional to the dielectric constant of the substrate material,the dielectric constant is smaller,the sensitivity is higher.The sensor only has good sensing performance when the thickness of the analyte is less than 18 ?m.The research results provide reference as the application of EIT metamaterials for refractive index sensing applications.The researches in this paper will help to understand the electromagnetic mechanism and control properties of EIT-like metamaterials,obtain the construction method of metamaterial structures,and develop some related applications based on EIT resonances.These results are expected to play a certain role in promoting further researches and applications of EIT-like metamaterials.