Two-Dimensional Photonic Topological Phases Based On Gyromagnetic Materials

Traditional optical principles restrict efficient optical transmission and limit the development of integrated optoelectronics,especially the processing of large capacity and high speed information,which can no longer meet the needs of current people.With the development of topological photonics,people can propose new schemes to regulate photon transmission from basic physics.With the development of topological photonics,people can propose new schemes to regulate photon transmission from basic physics.The topological edge state is an important medium for the construction of photon transmission waveguides because it is immune to impurity scattering and is not affected by defects and large Angle turns.In this thesis,photonic crystals with graphene lattice structure are constructed based on gyromagnetic material YIG.Topological phase transition processes of photonic crystals in different systems are explored by adjusting controllable phase transition parameters.The main work is as follows:1.Based on the band theory of plasmons,a surface wave optical crystal model is constructed using metal columns and gyromagnetic materials.The model has a graphene lattice structure.In order to make different sublattices have different lattice potentials,the spatial symmetry of the system is broken by using the height difference of metal columns in the z direction.By applying a z-polarized static magnetic field to YIG,the temporal inversion symmetry of the system is broken,and the unpaired single Dirac point and topological phase transition process are observed under the "competition" relationship between the two symmetry mechanisms.Finally,using the valley degree of freedom of photonic crystal,a valley dependent beam splitter of surface wave photonic crystal is designed.2.Based on the non-Hermitian photonic crystal theory,a photonic crystal model of lossing-induced topological phase transition was constructed using gyromagnetic materials and wave absorbent.The model is based on the lattice structure of graphene.Under the condition of breaking the spatial symmetry and temporal inversion symmetry of the system,loss is artificially introduced into the lattice points.The topological phase transition induced by the loss was observed by controlling the loss.Moreover,unpaired single Dirac points are theoretically observed.Based on the above work,the topological phase of photonic crystal is observed under two different physical backgrounds(Hermitian system and non-Hermitian system)based on gyromagnetic materials,and the complete phase transition process is observed by adjusting the phase transition parameters.Finally,the edge state transfer is tested experimentally.The above work enriches the study of photonic crystal topological phase and provides convenience for the construction of photonic devices.