Application Of Photonic Crystals In Controlling Directive Radiation And Electromagnetic Waves

Photonic crystals(PCs)are artificial periodic structures.PCs have been intensively studied in the past years because of their special band-structure and amazing electromagnetic properties.Magnetic PCs(MPCs)are PCs composed of ferromagnetic materials and have some special properties,such as the negative permeability,the surface magneto-plasmon,the negative refraction,the nonreciprocal properties induced by the broken time-reversal symmetry and so on.Based on these properties,some new application of PCs such as super lens,photon quantum effect and so on caused great interest recently.As PCs' ability of changing the dispersion characteristics of electromagnetic(EM)wave and controlling of EM wave,they have been applied to microwave and optical devices,such as antennas,filters and resonators.We focus on the ability of MPCs on controlling of the radiation and spread of EM waves,and study the application of MPCs in directive radiation and propagation of EM waves.We analyzed the radiation of line source within a hollow cylinder made of left-handed material,and discussed several factors that affected the performance,such as the topological structure of boundary of the structure,the position of line source,the size of the structure and so on.We designed and realized the antenna with self-biased MPCs,and analyzed the effect of PCs' factors.The antenna has simple structure and performs good.We theoretically and experimentally study the radiation of current line source embedded in ferromagnetic PCs.Our results demonstrate that by lowering the symmetry of the PC,the source radiation could be highly directive because the PC only allows the source radiating in one direction when it operates at the band edge of the PC.The source radiation also shows the broadband frequency tunability since the band structure of the PC changes under bias magnetic fields.The directive radiation and its frequency tunability are further demonstrated by experiments.We used transformation optics to design a gateway that can block EM waves but allows the passage of other entities.The gateway is realized by self-biased MPCs and performs well.The structure is simple and easy to realize.Simulations and experiments fit well,showing its ability to suppress EM waves in specific frequency.