Invisibility Cloak And Illusion Devices Based On Transformation Optics

In recent years,with the development of metamaterials and the theory of transformation optics,various functional devices have been proposed,such as well-known invisibility cloak and illusion devices.The theory of transformation optics originated in the electromagnetic field and was subsequently extended to manipulating other physical fields such as dc electric fields and thermal flow fields.The functional devices based on transformation optics face the problem of complex material parameters(inhomogeneous and anisotropic).This thesis aims to simplify the parameters of metamaterials and propose new functional metamaterials,including the following two works:(1)A polygonal thermal invisibility cloak with homogeneous material parameters is proposed.The material parameters of the polygonal thermal cloak are deduced using the coordinate transformation method and the implementation is suggested to use the multi-layered structure based on the effective medium theory.It is shown that the proposed thermal cloak only requires 4 types homogeneous and isotropic natural materials.The simulation results show that the proposed thermal cloak has an excellent cloaking performance under both transient and steady state conditions,demonstrating good robustness.In addition,the relationship between cloaking performance and the number of stratifications is discussed.It is found that the greater the number of layers,the closer its performance to the ideal invisibility cloak.(2)An optically controlled dc illusion device is proposed and experimentally demonstrated.First,based on the coordinate transformation theory,a square dc cloak was designed with homogeneous conductivity parameters.Then,based on circuit theory,the resistance network is used to equivalently realize the required conductivity material.Finally,a dc illusion device was realized by connecting photoresistors in the resistance network of dc cloak.It is shown that the dc illusion device acts as an invisibility cloak in dark field and acts as an illusion device in bright field.