  Progress on two-dimensional materials has shown that valleys, as energy
extrema in a hexagonal first Brillouin zone, provides a new degree of freedom
for information manipulation. Then valley Hall topological insulators
supporting such-polarized edge states on boundaries were set up accordingly. In
this paper, a two-dimensional valley photonic crystal composed of six tunable
dielectric triangular pillars in unit cells is proposed in the photonic sense
of a deformed Su-Schrieffer-Heeger (SSH) model. We reveal the vortex nature of
valley states and establish the selection rules for valley polarized states.
Based on the valley topology, a rhombus-shaped beam splitter waveguide is
designed to verify the valley-chirality selection above. Our numerical results
entail that this topologically protected edge states still maintain robust
transmission at sharp corners, henceforth providing a feasible idea for valley
photonic devices in THz regime.
