Research On Electromagnetic Transparent Metamaterials Based On Brewster Effect

Metamaterials are artificially engineered composite materials consisting of subwavelength unit cells arranged in periodic patterns,which can achieve peculiar electromagnetic properties that are not found in naturally occurring materials.In the past two decades,the researches on metamaterials have developed rapidly,not only revolutionized fields such as communication,imaging,remote sensing,and energy,but also spawned a series of new electromagnetic functional devices,such as super lenses,electromagnetic invisibility,and electromagnetic illusion.Based on the naturally occurring Brewster effect of TM polarized wave and the construction principles of metamaterials,this thesis studied the TE polarized and polarizationindependent Brewster effect respectively,and realized the TE polarized tunable broadband angular selectivity in terahertz band and the polarization-independent broadband angular selectivity in microwave band based on the above achievements.At the same time,this thesis broke the limitation of the traditional Brewster effect that can only occur at a specific angle,and realized the TM polarized and polarization-independent transparent subluminal and superluminal metamaterials with Brewster effect can be observed at all angles of incidence,which have been demonstrated to exhibit ideal invisibility in free space,providing a feasible solution to advance the practical application of transformation optics devices.The specific research work of this paper is as follows:1.Theory and design methods for transparent metamaterials.Firstly,the full transmission effect of TM polarized Brewster angle existing in naturally occurring materials was expounded,the relationship between the TE and TM polarized Brewster angle in magnetic materials and the corresponding electromagnetic parameters were derived,and the electromagnetic parameter form of materials with all-angle Brewster effect was obtained.Secondly,the construction principles and design methods of various metamaterials were summarized,and an extraction algorithm for calculating equivalent electromagnetic parameters were derived by using scattering parameters of normal and oblique incidence.Finally,algorithms for calculating the reflection and transmission coefficients of multi-layered materials under any angle and any polarized plane wave incidence were analytically calculated and programmed.The above content provides theoretical foundation,design methods,and numerical algorithms for the research in the following two chapters.2.Research on angular selective transparent materials based on the Brewster effect.To address the problem that angular selective transparent structures based on naturally occurring materials can only work for TM polarized waves,this thesis studied the designing method of TE polarized and polarization-independent broadband angular selective transparent structures.By introducing magnetic anisotropic broadband metamaterials and temperature-controlled dielectrics(strontium titanate)in one-dimensional photonic crystal stacks,a tunable broadband angular selective structure for TE polarized wave in the terahertz frequency band was designed.Furthermore,by introducing electrically and magnetically anisotropic broadband metamaterials in the photonic crystal stacks,a polarization-independent broadband angular selective transparent structure was realized and verified in the microwave frequency band.The above research solves the problem that the traditional broadband angular selective transparent structures can only work for TM polarized wave,providing a solution for achieving polarization-independent spatial filtering and radar anti-jamming.3.Research on all-angle transparent materials based on the Brewster effect.All-angle impedance matching transparent is the common requirement of the existing free-space transformation optical devices,to address this issue,this thesis carried out researches on allangle transparent materials based on the Brewster effect.By constructing metamaterials with three-dimensional adjustable electromagnetic parameters,and precisely controlling the dispersion of the constitutive parameters in each direction,this thesis realized TM polarized allangle transparent subluminal and superluminal materials that satisfy the condition of uniaxial perfectly matched layer model and all-angle Brewster effect.Based on the above materials,this thesis demonstrated ideal omnidirectional matching invisibility in space for the first time.Furthermore,based on the Fabry-Pérot resonance,this thesis realized polarization-independent all-angle transparent materials with all-angle Brewster effect,and verified the all-angle polarization-independent invisibility in space through full-wave simulations.The above researches solve the problem of phase shift in omnidirectional transformation optical devices and provide a solution for realizing ideal omnidirectional full-parameter transformation optical devices.