Design And Optimization Of Multifunctional Programmable Metamaterial Based On Inverse Design

Since metamaterials have some exotic properties that cannot be achieved by natural materials,and can more easily control the transmission characteristics of light,they are widely used in photonics and other fields.In order to enhance the ability of metamaterials to flexibly control electromagnetic waves,programmable metamaterial have been proposed and widely used.But they are mainly used to process electromagnetic waves in the terahertz and microwave bands,and only a small number of programmable metamaterials can process electromagnetic waves in the near-infrared band.However,such work often needs to construct metamaterial structures with different sizes and shapes to realize different functions,which makes the optical system consisted of these metamaterial structures have problems such as low reconfigurability,high complexity,large insertion loss and so on.To overcome these problems mentioned above,in this thesis,two multifunctional programmable metamaterials working in the near-infrared band are designed.And this thesis focuses on the research of these two multifunctional programmable metamaterials,and the related work completed is as follows:1.A two-dimension(2D)multifunctional programmable metamaterial working in the near-infrared band is designed.Its basic structure is fixed,but it has many basic units that can be binary coded to achieve different functions.This metamaterial structure is designed by using a direct binary search(DBS)algorithm to obtain some optical devices which can achieve six different functions.These functions include central-wavelength-tunable and bandwidth-tunable plasmon-induced transparency-like,central-wavelength-tunable single-peak absorption and distance-tunable double-peak absorption,as well as band-pass and band-stop filters.The spectrum accuracy is used to measure the closeness of the optimized spectrum to the target spectrum.The higher the spectrum accuracy,the closer the optimized spectrum is to the target spectrum.When implementing the six functions mentioned above,the maximum spectrum accuracies are 95.26%,95.26%,88.66%,76.04%,76.52%and 72.13%respectively.2.A three-dimension(3D)multifunctional programmable metamaterial working in the near-infrared band is designed.Compared with 2D multifunctional programmable metamaterial,3D multifunctional programmable metamaterial has a higher degree of spatial freedom.It can achieve the same function by fine-tuning the electromagnetic wave so that the generated spectrum is closer to the target spectrum.And the conventional DBS algorithm is improved to make it suitable for optimizing the 3D multifunctional programmable metamaterial.By using the modified DBS algorithm to optimize this structure,six functions that are the same as the 2D multifunctional programmable metamaterial are obtained.The maximum spectrum accuracies are 97.49%,97.49%,95.34%,86.38%,78.76%and 75%respectively.Compared with the optimization results of 2D multifunctional programmable metamaterial,when implementing the six functions mentioned above,the maximum increase of the spectrum accuracy is 11.03%.