Direct Observation of Corner States in Second-Order Topological Photonic Crystal Slabs

Recently, higher-order topological phases that do not obey the usual bulk-edge correspondence principle have been introduced in electronic insulators and brought into classical systems, featuring in-gap corner or hinge states. In this Letter, using near-field scanning measurements, we show the direct observation of corner states in second-order topological photonic crystal slabs consisting of periodic dielectric rods on a perfect electric conductor. Based on the generalized two-dimensional Su-Schrieffer-Heeger model, we show that the emergence of corner states roots in the nonzero edge dipolar polarization instead of the nonzero bulk quadrupole polarization. We demonstrate the topological transition of…

• NN
  National Natural Science Foundation of China

  Awards: 11704422, 61775243, 11761161002
• NS
  Natural Science Foundation of Guangdong Province

  Award: 2018B030308005