  Topological valley kink states have become a significant research frontier
with considerable intriguing applications such as robust on-chip communications
and topological lasers. Unlike guided modes with adjustable widths in most
conventional waveguides, the valley kink states are usually highly confined
around the domain walls and thus lack the mode width degree of freedom (DOF),
posing a serious limitation to potential device applications. Here, by adding a
photonic crystal (PhC) featuring a Dirac point between two valley PhCs with
opposite valley-Chern numbers, we design and experimentally demonstrate
topological valley-locked waveguides (TVLWs) with tunable mode widths. The
photoinc TVLWs could find unique applications, such as high-energy-capacity
topological channel intersections, valley-locked energy concentrators, and
topological cavities with designable confinement, as verified numerically and
experimentally. The TVLWs with width DOF could be beneficial to interface with
the exsisting photonic waveguides and devices, and serve as a novel platform
for practical use of topological lasing, field enhancement, on-chip
communicaitons, and high-capacity energy transport.
