Research On The Applications Of Terahertz Resonators In EIT And Absorbing Based On Metamaterial

Metamaterials are artificially designed electromagnetic materials which composed of sub-wavelength scale unit cells arranged in periodic order.With the rapid development of Terahertz radiation and micro-nanofabrication technology,various devices based on metamaterial such as EIT resonators,absorbers and polarizer,etc.have been successfully applied in terahertz regime.Recently,analogue of electromagnetically induced transparency based on metamaterial has attracted tremendous attention due to the possibility of simplifying the extreme experimental conditions in quantum field.However,it is rarely reported to use the complementary metamaterials to achieve the EIT phenomenon in THz field and the dissertation makes a further supplement to it.Moreover,our attention is paid to the study of THz absorbers based on highly doped silicon,which is considered as a novel metamaterial.These THz absorbers have important applications in THz detection and imaging.This dissertation is divided into three parts and the material works are organized as follows:(1)A terahertz metamaterials fabrication technology based on laser direct writing together with related techniques was studied.The main work includes spin coating process,laser direct writing technique and basic principles of magnetron sputtering metallization.We also give a description of the Micro Lab: SVG-4A100 laser direct writing system in detail,including basic working principles and operational procedures.(2)The analogue of regular phenomenon of electromagnetically induced transparency(EIT)with one transmission peak is achieved in a simple complementary metamaterial consisting of two detuned resonators(Slot).Finite element method(FEM)are carried out to analyze the EIT effect,a typical transparent window is appeared at the frequency of 0.625 THz.This phenomenon will be changed to demonstrate dual peaks when a small gap is present between two detuned resonators in the metamaterial.It is the destructive interference among gap-induced extra pathways leading to the phenomenon of dual-peak EIT-like effect.By shifting longitudinally the gap position relative to the center of the SRs will lead to an efficient engineering of the EIT-like effect.This novel dual-peak analogue of EIT with new flexibility may provide potential applications in sensors,integrated THz devices and plasmonic switches.(3)We experimentally demonstrate that at terahertz frequencies perfect plasmonic absorbers made on a highly doped silicon platform can be easily realized,exhibiting near-zero dips in the reflection spectra.The unit cell of the absorber consists of a dielectric layer of SiO2 film sandwiched between a highly doped silicon wafer and the copper structures,in the form of either one-dimensional stripe array or two-dimensional cross array.The reflection spectrum of the proposed absorbers are characterized using a terahertz time-domain spectroscopy system and the experimental results are in good agreement with numerical simulations.The dependence of the absorption on the THz polarization for both the 1D and 2D absorbers are also investigated.The high performance together with the easy fabrication processes presented in this paper show that the plasmonic absorber holds high prospect in terahertz applications.