【作者】 张敏；

【导师】 延凤平；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2021， 硕士

【摘要】 电磁诱导透明是一种发生在三能级原子系统中的量子干涉效应,能使不透明的介质变为透明,使介质对探测光的吸收几乎为零。伴随该效应产生的慢光效应、折射率骤增等特性使其在光信息存储、折射率传感等领域有着巨大的应用价值。在传统的原子系统中,实现该效应通常需要超低温、强光抽运等严苛的实验环境,而利用超材料这种人工合成的电磁材料来模拟电磁诱导透明,不仅克服了这一困难,而且能够通过光控、温控、电控等方式实现可调的电磁诱导透明窗口,这大大拓展了电磁诱导透明的应用前景。本文在太赫兹频段内,对电磁诱导透明超材料展开研究,根据超材料实现电磁诱导透明效应的两种耦合方式,分别设计了以金属和石墨烯为主控材料的超材料结构,并仿真分析了其电磁响应特性与性能。主要研究内容如下:设计了一种明暗模耦合的电磁诱导透明超材料结构。通过四个开口谐振环与平面闭合方环的三维耦合,该结构于1.21 THz、1.46 THz、1.61 THz与1.98 THz产生了四个电磁诱导透明窗口,且谐振强度均达到0.9左右。通过拆分对比单元结构及表面电磁场分布,深入研究了实现多波段电磁诱导透明效应的耦合机理。讨论了超材料中开口谐振方环的开口大小、闭合方环尺寸对EIT强度与带宽的影响。分析了该结构在慢光效应与折射率传感方面的应用性能。设计了一种明明模耦合的电磁诱导透明超材料结构。通过条形石墨烯结构与T形石墨烯结构实现明明模耦合作用,产生电磁诱导透明窗口。通过外加偏置电压改变石墨烯的费米能级,对透明窗口进行调节。探讨了超材料中单元周期、条形与T形石墨烯结构宽度、入射波极化角对电磁诱导透明传输响应的影响。调节石墨烯的费米能级,研究了该结构的群延时、折射率灵敏度、调制深度等性能指标。仿真分析表明,上述两种超材料均能够于太赫兹波段实现电磁诱导透明效应。第一种三维超材料结构能够实现多频点的高强慢光效应,其群折射率可达289.4,还具备多频段的高折射率灵敏度(658 GHz/RIU);第二种石墨烯超材料结构能够实现群延时高达173.13 ps的可调慢光效应以及折射率灵敏度为562.5 GHz/RIU的动态调控。因此,两种结构在光缓存与折射率传感领域都有良好的应用性能,为未来太赫兹器件的设计提供了新思路。更多还原

【Abstract】 Electromagnetically induced transparency is a quantum interference effect that occurs in a three-level atomic system,which can make an opaque medium transparent and make the medium’s absorption of probe light almost zero.The slow light effect and sudden increase in refractive index accompanying this effect make it of great application value in the fields of optical information storage and refractive index sensing.In traditional atomic systems,the realization of this effect usually requires harsh experimental environments such as ultra-low temperature and strong light pumping.The use of artificially synthesized electromagnetic materials such as metamaterials to simulate electromagnetically induced transparency not only overcomes this difficulty,but also The adjustable electromagnetically induced transparent window can be realized through light control,temperature control,electric control,etc.,which greatly expands the application prospect of electromagnetically induced transparency.In this paper,the electromagnetically induced transparent metamaterials are studied in the terahertz frequency band.According to the two coupling modes of metamaterials to achieve electromagnetically induced transparency effects,the metamaterial structures with metal and graphene as the main control materials were designed,and their electromagnetic response characteristics and performance were simulated and analyzed.The main research contents are as follows:1、An electromagnetically induced transparent metamaterial structure coupled by bright and dark modes is designed.Through the three-dimensional coupling of four open resonant rings and a planar closed square ring,the structure produced four electromagnetically induced transparent windows at 1.21 THz,1.46 THz,1.61 THz and1.98 THz,and the resonance intensity reached about 0.9.By splitting and comparing the cell structure and the surface electromagnetic field distribution,the coupling mechanism to realize the multi-band electromagnetically induced transparency effect is deeply studied.The influence of the size of the opening of the open resonant square ring and the size of the closed square ring on the strength and bandwidth of the EIT in the metamaterial is discussed.The application performance of the structure in slow light effect and refractive index sensing is analyzed.2、An electromagnetically induced transparent metamaterial structure with explicit mode coupling is designed.Through the strip graphene structure and the T-shaped graphene structure,the bright mode coupling effect is realized,and an electromagnetically induced transparent window is produced.The Fermi level of graphene is changed by applying a bias voltage,and the transparent window is adjusted.The effects of unit period,strip and T-shaped graphene structure width,and incident wave polarization angle on the response of electromagnetically induced transparent transmission in metamaterials are discussed.The Fermi level of graphene was adjusted,and the group delay,refractive index sensitivity,modulation depth and other performance indicators of the structure were studied.Simulation analysis shows that both of the above-mentioned metamaterials can achieve electromagnetically induced transparency in the terahertz band.The first three-dimensional metamaterial structure can achieve multi-frequency high-intensity slow light effects,and its group refractive index can reach 289.4,and it also has multi-band high refractive index sensitivity(658GHz/RIU);the second graphene metamaterial structure can Realize the adjustable slow light effect with a group delay of up to 173.13 ps and the dynamic adjustment of the refractive index sensitivity of 562.5GHz/RIU.Therefore,both structures have good application performance in the fields of optical buffer and refractive index sensing,and provide new ideas for the design of terahertz devices in the future.更多还原