ABSTRACT
Topological properties of electromagnetic waves propagating in periodic systems have received considerable attention recently. Based on the band structure analysis, a class of surface states can be interpreted from the bulk-interface correspondence if a topological phase transition takes place in photonic band gap materials. In addition to the band structure analysis, the topological properties can be manifested in other parameter spaces. Here, we will introduce some recent works in topological photonics both within and beyond the band structure analysis, including: 1) SSH model in the 1D electromagnetic system and “valley-polarized” interface states in the 2D systems; 2) bound states in the continuum (BICs) in the photonic crystal slab. As an example of topological photonics concepts beyond the band structure analysis, a new mechanism of perfect reflection is proposed for dielectric medium beyond the total internal reflection and band gaps. It can be determined by the topological vortex of transmission coefficient with a non-zero winding number in parameter space. Based on the coherent perfect reflection, a generalized waveguide condition is derived analytically. Our findings may have many potential applications in the guided-wave optics.
BIOGRAPHY
Prof. Dezhuan Han obtained his BSc degree (2001) from Fudan University, Master degree (2003) from New York University, and PhD degree (2006) from Fudan University. Before he joined Chongqing University, he worked as a Postdoc at The Hong Kong University of Science and Technology. His research interest mainly focuses on photonic crystals, plasmonics, and metamaterials. He has published over 40 peer-reviewed articles in the journals including Nat. Commun., Phys. Rev. Lett., Phys. Rev. B, etc.