Phase Modulation Of Surface Wave Based On Dielectric And Magnetic Composite Metamaterials

Metamaterials is a kind of artificial composite material,which is composed by subwavelength resonant building blocks arranged in a periodic or nonperiodic configuration.It offers exotic electromagnetic properties which are not possessed by natural materials.Therefore,an electromagnetic wave can be molded nearly arbitrarily,giving rise to a variety of interesting phenomena such as negative refraction,electromagnetic invisibility cloak,and polarization conversion.Phase is one of the basic physical quantities to characterize electromagnetic waves,and phase modulation is always a hot topic in the optics.Traditional optical elements can control the phase by either changing the thickness of the device or using the refractive index difference of natural materials.By use of magnetic metamaterials,the phase modulation of a surface wave can be achieved with high efficiency and flexible tunability.The subwavelength dielectric waveguide constructed with the dielectric-rod chain is considered,which can not only overcome the material loss of metal surface plasma waveguide but also exhibits the characteristics of extremely low radiation loss.In this thesis,by combing the subwavelength dielectric-rod-chain waveguide and magnetic metamaterial,we have constructed composite metamaterials which is employed to implement the phase modulation of the guided surface wave.The framework and the obtained results are as follows:In chapter one,the research progress,the electromagnetic properties,and the related applications of metamaterials are briefly introduced.The theoretical approach and simulation methods are presented in chapter two: Mie scattering theory for rigorous solution of single particle scattering;Multiple scattering theory(MST)for calculating the photonic dispersion curves and the electromagnetic fields of composite structure;and the effective constitutive parameters of the magnetic metamaterials are analyzed and calculated by the effective medium theory(EMT)in the long wavelength limit.In chapter three,the working frequency range of the dielectric array is adjusted to the concerned microwave regime according to the scaling invariance of the dielectric system.Meanwhile,two the magnetic metamaterial slabs consisting of an array of the ferrite rods arranged in the square lattice are cladded symmetrically on both sides of the dielectric array,thus constituting the dielectric and magnetic composite metamaterials.By using the MST,the photonic band diagrams and the electric field profiles are calculated,based on which the parameters of the supercells in the composite structure are optimized.Then,the phase profile of the surface wave in the composite metamaterials are simulated,the phase modulation in the range of 0-2π is implemented by tuning the bias magnetic field(BMF).The dependence of the output phase on the length has been analyzed as well so that the optimal size of the composite structure can be acquired.In chapter four,we have investigated the transport efficiency of the surface wave,which is shown to be dependent on the magnitude of the BMF.First,the BMF at the input side is chosen to minimize the reflection of the surface so that the transport efficiency is improved.Then,the gradient is introduced in the BMF with its magnitude at the input side is fixed.As a result,the output phase can be flexibly tuned by the gradient,adding an additional degree of freedom.In the end,the conclusion is summarized and the outlook is also presented in the last chapter.