Study On One Way Transmission Characteristics Of Electromagnetic Wave In Magnetic Photonic Crystal

Magnetic materials have been widely used in the microwave and optical information technology.They play an important role in realizing miniaturization,adjustment,impedance matching of microwave and optical device.They also play an irreplaceable important role in the transmission of the control signal isolator,circulation and phase shifter applications.Magnetic photonic crystals(MPCs)are composed of magnetic material.Under the bias magnetic field,permeability is an anisotropy and dispersion tensor.MPCs have magnetic resonance,magnetic surface plasmon,breaking time reversal symmetry and the consequent nonreciprocity.Recently,these special characteristics make it much attractive.This thesis focused on the one-way edge transmission and body state nonreciprocal propagating characteristics of electro-magnetic(EM)waves in magnetic photonic crystals.Through theoretical calculation,simulation and experimental verifications,the main results are attained as follows:(1)The band structures of two-dimensional(2D)gyromagnetic photonic crystals are analyzed by a modified finite difference time domain(FDTD)method.A special implementation is used to tackle the magnetic constitution equation.This method avoids the discretizing complexity in the time domain caused by nonlinear frequency dependence of anisotropy permeability tensor,and therefore keeps the fully explicit nature of the original FDTD method.Our implementation is proved by the band structure calculations using other methods and the transmission measurements of 2D gyromagnetic PC involving circular ferrite rods and square rods.(2)We theoretically demonstrate that electromagnetic waves can self-collimated propagate in photonic crystals fabricated using ferrite rods in magnetized states.We discuss the influence of fill factor,duty ratio factor.etc.Based on the different transmission characteristics of the beam in the photonic crystal,we design the 90 degrees bending,T type beam splitter.(3)Through broken space symmetry of ferrite basis cell,we investigate self-collimation body state nonreciprocal propagating properties in two-dimensional MPCs fabricated by semi-cylinder rods.Direction of the beam realizes gradual change along with changing the bias magnetic field.Ultimately,by applying the bias magnetic field in a complex configuration,the self-collimated one-way wave beam can be bent into arbitrary trajectories within the photonic crystal,providing a new avenue for controlling wave beams.Besides,nonreciprocal spatial wavelength division can be arrived without introducing any corrugations inside the structure.(4)We propose a two dimensional compound lattice MPCs,which consist of two interpenetrating triangular lattices.This kind of lattice simultaneously breaks the space and time symmetries.Due to asymmetry of its photonic band structure,its bulk modes support one-way propagation for group velocity,and it has negative refraction characteristics in the interface.The optical transformation does not change the distribution of off-diagonal imaginary elements in the tensor permeability,so the physical properties of time symmetry broken can be maintained.Numerical results show incident waves can pass through the bending waveguide without any reflections in one direction,but totally be reflected in opposite direction.(5)We study the unidirectional edge characteristics of MPC slab.When the original degeneracy point in k space is lifted below the light cone,we analyzed the topology edge state and the corresponding electromagnetic wave one-way transmission characteristics.We discussed the influences of permittivity and thickness of the substrate on one-way edge states.And we demonstrate that one-way electromagnetic modes could be sustained by the zigzag edge of the slab.(6)We proposed a class of nonreciprocal bulk modes based on a chain of gyromagnetic rods with the asymmetric prime cell.The one-way body state transmission characteristics of these chains are demonstrated by calculating band structure,simulating and experiments.Its transmission characteristics are analyzed and discussed.These chain MPCs have many excellent performances such as simple structure,tunable,design,flexible shape.