Novel Electronmagnetic Functional Materials and Photonic Topological Realizations

Explorations of artificial materials for manipulating electromagnetic waves have found its prominent advantages in a wide range of applications. These artificial electromagnetic materials have aroused our extensive interest, such as photonic crystals, metamaterials, plasmonic nanostructures, and PT symmetric electromagnetic materials. In this thesis, we investigate various electromagnetic functional materials for applications and the realizations of topological effects analogy to condensed matter physics based on artificial electromagnetic materials. We report the largely enhanced transmission of electromagnetic waves through periodic subwavelength apertures in an opaque plate by inserting connected ring resonators through apertures at selected microwave frequencies. Two typical structures of connected ring resonators we proposed in this work can achieve 0.8 or even higher transmittance both in simulations and experiments. In addition, one of them can serve as a polarization converter with an arbitrary rotation angle and high transmission efficiency simultaneously. We have also proposed a multi-band metamaterial perfect absorber of deep-subwavelength thickness at microwave frequencies with near-unity absorption coefficient. This planar metamaterial is composed of periodically arranged concentric metallic rings and a continuous metallic grounded plate which are separated by a lossy dielectric layer. The origin of the induced multi-band perfect absorption is attributed to the multiple impedance matching conditions to free space and can be achieved through tuning the constitutive relations by several electromagnetic resonances. Moreover, the absorption could be enhanced and broaden by overlapping the modes of different rings. The absorption is identical for arbitrary polarizations due to its rotational symmetry and remains over 90% with the oblique angle of incidence 60â—¦. Then, we have studied that the surface plasmon can be supported on graphene sheets as the Dirac electrons oscillate collectively. With the tight-binding model for graphene plasmons’ couplings, the Zak phases of periodic graphene sheet arrays are obtained for different configurations. Analogous to Su-Schrieffer-Heeger (SSH) model in electronic sys- tems, topological edge plasmon modes emerge when two periodic graphene sheet arrays with different Zak phases are connected. These plasmonic edge states in multilayer graphene systems can be further tuned by electrical gating or chemical doping. Next, we investigated the band properties of 2D honeycomb plasmonic lattices consisting of metallic nanoparticles with and without normal magnetic field. By means of the coupled dipole method and quasi-static approximation, we theoretically analyze the band structures stemming from near-field interaction of localized surface plasmon polaritons for both the infinite lattice and finite ribbons. For a fixed k∥ of in-plane polarized modes, we derived the bulk-edge correspondence, namely, the relation between the number of flat edge states, Zak phase of the bulk band and the winding number associated with the bulk hamiltonian and verified it through four typical ribbon boundaries. Finally, we proposed an artificial structure at microwave frequencies can mimic the couplings between real plasmonic nanospheres and electron hoppings and experimentally demonstrate a zigzag chain can support topological edge states at two ends. Moreover, this two topological edge states with perpendicular dipole moment can be selectively excited with different incident polarizations. These novel artificial electromagnetic materials extend the range of application and can also serve as a good experiment platform through analogies with other experimentally unaccessible systems.