Nonlinear Topological Surface States in Meta-Crystals
Technical Report,01 May 2016,31 Jan 2017
State University of New York (SUNY) at Buffalo Amherst United States
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Photonics offer a unique platform for realizing many remarkable topological phenomena at room temperature and without strong magnetic field and, moreover, may bring them to the domain of practical applications, including robust energy transport in compact, integrated photonic devices, all-optical circuity, and optical communication systems. For many of these applications, scattering-free propagation combined with reconfigurability and the ability to control the propagation of light is essential. Nowadays, the majority of proposed photonic topological insulators operate in a fixed wavelength range and their mode of operation and topological properties cannot be dynamically reconfigured. The realization of actively reconfigurable photonic topological structures remains a grand challenge. This STIR project allowed us to develop a set of tools, both analytical and numerical, as well as an experimental setup and fabrication procedures to study various types of topologically protected light propagation. These tools have been applied to design actively reconfigurable photonic topological insulators based on photonic meta-crystal built of optically nonlinearly, electrically or thermally tunable meta-molecules designed. We numerically studied a reconfigurable photonic topological insulator based on photonic crystal design to realize the photonic analogue of the spin-Hall effect. The reconfigurability is facilitated by immersing the photonic crystal into a nematic liquid crystal background, as shown in Fig. 1. With the help of an external field applied to the liquid crystal, its molecules can be reoriented, causing variation in background refractive index and shifting the spectral position of edge states. However, topological properties of this initial design are set by design, i.e. the topological invariant, the Chern number, determining the number of edge states is fixed.
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