Metamaterials and Topology Enabled Light-Matter Interactions and Photonic Devices

Abstract

Engineered materials currently play a central role in the fields of nanophotonics and nanoelectronics. Recent advances in nanofabrication enabled exciting opportunities for light manipulation that were never possible before. Wherein this dissertation, I investigate different kinds of engineered optical materials, including metamaterials, metasurfaces and topological photonic crystals. First, I discuss my theoretical studies of the process of second harmonic generation in negative index metamaterials with optical vortex beams. The negative index of refraction enables a a novel regime of backward phase-matching, where the interacting waves energies propagate in opposite directions. I have demonstrated that the vortex beam launched from the positive linear material changes its helicity in the negative index metamaterial, while the generated second harmonic wave propagates backward with simultaneously doubled frequency, doubled optical angular momentum, and reversed rotation direction of the wavefront. The second part of my dissertation is devoted to investigation of all-dielectric metasurfaces for beam steering and beam shaping. Metasurfaces are two-dimensional versions of metamaterials that are easier to fabricate than their three-dimensional counterparts and that also enable low-loss operation due to their small optical thickness. Despite their subwavelength thicknesses, they enable full control on amplitude phase and polarization of light. In particular, I have experimentally demonstrated highly-efficient all- dielectric metasurface with full 0-to-2π phase control at near-infrared wavelengths that enable vortex beam converter and beam deflector with efficiencies of 45% and 36%, respectively. In the third part, I study topological photonic crystals. Topological photonics is posed to improve the efficiency of photonic devices by eliminating parasitic scattering losses due to so-called topological protection. Thus, these materials offers unprecedented opportunity to avoid the loss on structural imperfections and disorders, facilitating robust light propagation. Specifically, I demonstrate lossless (scattering-free) light propagation around sharp turns in photonic crystal slab with non-trivial topology. In addition, two tunability mechanisms of the photonic topological insulators enabled by electrically tunable liquid crystal properties and optically tunable free-carries excitation in semiconductor material. The dynamic control on topological edge states is demonstrated theoretically and experimentally for liquid crystal and free carrier excitation approaches, respectively. Finally, I investigate optical properties of topological photonic crystal ring resonators. I characterize the limitation of topological protection for the case of in-plane light scattering and demonstrate a sup- pression of out-of-plane scattering as compared to conventional hollow W1 photonic crystal ring resonator.