  The realization of topological edge states (TESs) in photonic systems has
provided unprecedented opportunities for manipulating light in novel manners.
The Su-Schrieffer-Heeger (SSH) model has recently gained significant attention
and has been exploited in a wide range of photonic platforms to create TESs. We
develop a photonic topological insulator strategy based on SSH photonic crystal
nanobeam cavities. In contrast to the conventional photonic SSH schemes which
are based on alternately tuned coupling strength in one-dimensional lattice,
our proposal provides higher flexibility and allows tailoring TESs by
manipulating mode coupling in a two-dimensional manner. We reveal that the
proposed hole-array based nanobeams in a dielectric membrane can selectively
tailor single or double TESs in the telecommunication region by controlling the
coupling strength of the adjacent SSH nanobeams in both vertical and horizontal
directions. Our finding provides an in-depth understanding of the SSH model,
and allows an additional degree of freedom in exploiting the SSH model for
integrated topological photonic devices with unique properties and
functionalities.
