Manipulation Of Electromagnetic Waves Using Zero-index Photonic Crystal And Medium

Zero-index medium is a peculiar type of metamaterials whose refractive index is approaching zero.Owing to the homogenous field distribution and infinitely large wavelength inside zero-index medium,wide diversity of applications,including cloaking,absorption,directive emission,tunneling waveguides,electromagnetic flux control are suggested to be realized using zero-index medium.Among all zero-index medium design,photonic crystals with Dirac dispersion were found to have simultaneous effective zero permittivity and permeability.Low in loss using pure dielectric and easy to fabricate,zeroindex photonic crystals are proven to be a convenient platform to demonstrate zero-index related applications.In chapter 1,we discuss the classification and some fundamental properties of zero-index medium.We then introduce in details how to manipulate the band diagram of photonic crystal to realize photonic crystal with Dirac cone dispersion,i.e.zero-index photonic crystal,which is the material background of this thesis.A short introduction of our microwave field mapping platform is also included for readers to have a better understanding of our experimental system.Lastly,we briefly summarize all works conducted.In chapter 2,we introduce our work to realize a new cloaking device.Zero-index medium can efficiently control the electromagnetic flux and at the mean time preserve the incident phase information.Metasurface can manipulate the phase of incident and exit electromagnetic waves of the cloaking device.By combining zero-index medium and metasurface,a metasurface cloak in transmission geometry is realized and demonstrated in microwave experiments.This novel design scheme not only avoids the complicated inhomogeneous material distributions required by transformation optics,but also can largely decrease the size of cloaking device,indicating its promising application perspective.In chapter 3,we examine the criteria to achieve coherent perfect absorption using zeroindex medium.We found that by embedding a lossy defect with designed properties inside a zero-index medium,a new type of coherent perfect absorption can be realized,lifting the stringent two-port incidence restriction in traditional coherent perfect absorption design.More degrees of freedom to control the absorption rate are also provided.Good consistence can be found between our numerical simulations and microwave experiments where good coherent perfect absorption effects are obtained.In chapter 4,we discuss theoretically the possibility to extend the propagation angle of D’yakonov surface wave using anisotropic zero-index medium.Though our results discovered that the propagation angle of D’yakonov surface wave was not boosted using anisotropic zero-index medium,by optimization,we find that if certain properties of the materials to form the interface allowing D’yakonov surface wave can be satisfied,its propagation angle can be largely increased.In the last chapter 5,we summarize our major contributions and future research plans.