Research On Tunable Electromagnetically Induced Transparency Based On Metamaterials

In the three-level atomic energy level system,there is an important quantum interference phenomenon,that is,the phenomenon of electromagnetically induced transparency（EIT）.This phenomenon is manifested as an additional transparent narrow-band transmission window in the original wide absorption area of the transmission curve.And within the narrow-band transparent transmission window,the phase of the transmission curve will change sharply.The characteristics of narrow-band transparent transmission window and abrupt phase change make electromagnetic induced transparency have a wide range of application prospects in slow-light device design,sensor device unit design,optical storage device design,quantum switch device manufacturing and other fields.However,it is a pity that the harsh experimental environment,such as low temperature and high-intensity pump laser conditions,imposes great restrictions on the application of electromagnetically induced transparency in the actual environment.In order to solve these problems,a means of using metamaterials,that is,electromagnetic metamaterials,to simulate the electromagnetically induced transparency phenomenon in a simpler environment came into being.In order to differentiate from the traditional EIT phenomenon in the field of quantum interference,this electromagnetically induced transparency-like phenomenon realized by electromagnetic metamaterials is also called electromagnetically induced transparency-like EIT-like by researchers.The method of realizing EIT-like through metamaterials was first realized in the terahertz band by researchers from the X.Zhang research group.Through this realization method,researchers can obtain electromagnetic-induced transparency at room temperature without the need for a high-intensity pump laser excitation source.More importantly,the achievable frequency band of EIT-like can be moved from optical band to terahertz and microwave band,which greatly facilitates the application of EIT-like in the communication field.And by changing the size of the structure in the electromagnetic metamaterial unit,the coupling strength between the resonant units and other related parameters,the EIT-like transparent transmission window band required under different application conditions can be easily obtained.With the in-depth study of using metamaterials to achieve EIT-like,the research focus in recent years has mainly focused on achieving EIT-like tunability.In most studies,the tunable properties are mainly achieved by changing the shape of the unit structure,such as the size or opening direction;or by tunable materials,such as photosensitive silicon,graphene,and vanadium dioxide.Focusing on the research content that has been achieved so far and the existing shortcomings,this thesis mainly launched the following work:First,in order to make full use of the incident magnetic field,we designed a bright-bright mode metamaterial based on simultaneous electromagnetic excitation to achieve EIT-like.The unit structure mainly includes a metal block that can be directly coupled to the incident magnetic field and a metal strip that can be directly coupled to the incident electric field.At the same time,miniaturization is achieved.Such an implementation method greatly suppresses the scattering loss,so that the finally obtained EIT-like has low loss characteristics.In addition,because the overall unit structure is symmetrical,the EIT-like also has polarization insensitive characteristics.Further,in order to analyze the coupling process,apart from analyzing the surface current and magnetic field distributions at the three characteristic points of the transmission curve（two transmission troughs and one transmission peak）,we also use the linear coupling Lorentz model to verify the correctness of our analysis.Finally,we also compared the low-loss characteristics and the large group delay characteristics between different unit models to confirm our analysis.Inspired by frequency reconfigurable antennas,in this article,we use solid-state plasma（SSP）to achieve tunable EIT-like.The solid plasma here is formed on the Si-based semiconductor PIN tube.By applying a bias voltage to the metal contact of the semiconductor PIN tube,the carrier concentration（electron concentration and hole concentration）in the semiconductor PIN tube can reach 10¹⁸cm^-3.At this time,the solid plasma unit formed based on the semiconductor PIN tube can achieve the adjustment from the medium state to the metal-like state can be used as a radiation unit.We first designed a single PN junction Si-based semiconductor PIN tube,and on this basis,expanded the design of a multi-PN junction Si-based semiconductor PIN tube.Both types of PIN tubes can be used to form solid plasma through verification and analysis.Then,we combined solid-state plasma with the designed metamaterials,and finally realized the EIT-like tunability through using continuous and discrete solid-state plasma units,respectively,and compared and analyzed the results of using vanadium dioxide to achieve the tunable characteristic.