[26p-E303-1~10] 3.11 Photonic structures and phenomena

▲ [26p-E303-4] Design of an Optical Cavity in Quadrupole Topological Photonic Crystal Slabs

〇(M2)Guangtai Lu^1,2, Yasutomo Ota³, Satoshi Iwamoto^1,2 (1.RCAST Univ. Tokyo, 2.IIS Univ. Tokyo, 3.Keio Univ.)

Keywords:quadrupole topology, photonic crystals, topological photonics

Quadrupole topological insulators (QTIs), exhibiting gapped edge states and in-gap robust corner states, have been widely studied in various classical wave systems. These QTIs have been designed and analyzed based on tight-binding models with negative intersite couplings, which cannot be applied directly to photonic crystals (PhCs). This had made it difficult to realize quadrupole topological PhCs. Recently, post-based PhCs exhibiting quadrupole topological phase, not based on the tight-binding model, have been proposed in the microwave regime. However, no design of quadrupole topological photonic structures that can be realized in a PhC slab, which is widely used in nanophotonics, has been reported. In this work, we design quadrupole topological PhC slabs and an optical cavity based on them. We confirm that our PhCs have a quantized quadrupole momentum and a corner state supporting a quality factor Q as high as 8,000 is observed. We expect that our results promote the research of higher-order topological phase in nanophotonics platform