Topological edge states (TESs) and topological corner states (TCSs) in
photonic crystals (PCs) provide an effective way to control the
propagation and localization of light. The topological performance of
integrated photonic devices can be improved by introducing the basic
structural unit of photonic quasicrystals (PQCs) into PCs. However,
the previous works arranged the basic structural unit of Stampfli-type
and 12-fold Penrose-type photonic quasicrystals into triangular
lattices, which have a complex structure and allow light to only
propagate around 60° or 120° corners, limiting their applications. In
this paper, a Penrose-square PC is proposed, which realizes both TESs
and TCSs, and light successfully propagates around 90° corners. This
work may reduce the difficulties encountered in the preparation of
topological photonic crystals (TPCs) structured by arranging the basic
structural units of PQCs periodically. It also provides a new, to the
best of our knowledge, platform for studying TPCs and new ideas for
improving the performance of integrated photonic devices.