Effect of truncation on photonic corner states in a Kagome lattice

We theoretically present a simple nanophotonics platform, where the photonic corner states can be obtained in high frequencies. For the breathing Kagome lattice with three bearded truncations, we show that a pair of bonding and anti-bonding corner states can be observed in the gapped bulk bands, even for a topologically trivial lattice. In particular, this anti-bonding corner state is totally embedded in the bulk modes for topologically non-trivial structures, forming a bound state in continuum. We further verify that these corner states are protected by the symmetry and can be excited by merely one point source, even in a loss system. The newly found corner modes may expand our understanding of the high-order corner modes in a more general framework, involving both topology and symmetry. (C) 2019 Optical Society of America