Manipulating Electromagnetic Wave Propagating By Magnetic Photonic Crystals:A Theoretical And Experimental Investigation

In the past decades,photonic crystals(PCs)have been intensively studied because of their amazing capability of controlling light propagating.As a subclass,the magnetic photonic crystal(MPC)made of ferromagnetic materials has greatly promising applications especially with its magnetic characteristics.Except for the Bragg gap caused by periodic structure,MPCs own other special properties,including the negative permeability,the surface magneto-plasmon,the negative refraction,the nonreciprocal properties induced by the broken time-reversal symmetry and so on.Recently,with respect to the deeper researches on metamaterials and photon quantum effect,MPCs have been attracting more and more attentions.Compared to the relatively mature knowledge system of PC,MPC needs a further and deeper research,especially on the exotic phenomena analog to the electron system,which has broad prospects and application values.Up to now,the research is usually concentrated on the microwave frequency range,where the ferromagnetic materials have a quick response to bias magnetic field.With the advantage of magnetic tenability,fast response,high resistivity of ferrites,such magnetic photonic crystals have been realistically used in different application fields,such as new electromagnetic devices,electromagnetic communications and medical therapy.This thesis focuses on the manipulations of electromagnetic(EM)wave by MPCs,where the EM quantum Hall effect,one-way propagation,surface magneto-plasmon and left-handed transmission are investigated.Studied both theoretical and experimental study,we obtain the following results:(1)The EM chiral edge states(CESs)analog electronic integer quantum Hall effects have been studied.At the very first time,the self-guiding CESs was realized and the one-way transmission has been observed at the surface of truncated MPC.(2)The chiral edge states originated from the magnetic surface plasmon resonance are studied.It has been found these chiral edge states support one-way propagation but insensitive to the edge shape.Base on this special feature,the subwavelength one-way waveguide of arbitary shape is proposed and realized in experiments,which providing a new way to manipulating EM waves.(3)Magnetically tunable left-handed material is demonstrated in the composite of nested arrays of magnetic materials and metallic lines.The study gives the first unambiguous and direct experimental evidence to the tunable magnetic left-handed materials.(4)The characteristics of bandgaps in MPC have been studied systematically both in the theory and experiments.This thesis is organized as follows:Chapter 2 focuses on mechanism and characteristics of bandgaps in MPCs.By calculating band diagrams and measuring the transmission coefficient,the influence of lattice constant,filling ratio,bias magnetic field,lattice type,etc.to the frequency and bandwidth of Spin and Mie band gap has been studied.Chapter 3 concentrates on the EM quantum effect.At the very first time,the self-guiding chiral EM edge states have been demonstrated in experiment,which exists along the zigzag edge of a honeycomb magnetic photonic crystal.The edge states are shown to possess unidirectional propagation characteristics that are robust against various types of defects and obstacles.In particular,without requiring an ancillary cladding layer,such self-guiding chiral edge states are more directly analog of electron integer quantum Hall effect.Chapter 4 presents magneto-plasmon mechanism to realize EM one-way propagation.With help of the surface magneto-plasmon,we build a nonreciprocal system,in which EM wave can propagate along only one direction above the Mie resonance frequency,corresponding to another kind of chiral edge mode.Although EM waves transport in opposite directions below the Mie resonant frequency,they propagate nonreciprocally.After lots of simulations and experimental results,it has been found these magneto-plasmon one-way surface states are insensitive to the edge topology,showing a big difference from topological edge states in chapter 3.With this feature,some one-way sub-wavelength bend waveguides with an arbitrary bend angle are realized.The robustness of this unidirectional propagation is also proved by the experiments.Chapter 5 presents the two dimensional periodic composite made of ferrite rods and metallic wires.The composite is both theoretically and experimentally proved having a left-handed material(LHM)regime which is tunable by the bias magnetic field.