▎ 摘　　要

The Dirac singularity in 2D graphene structures theoretically allows pseudo-diffusive transport of photons or phonons, under which condition the energy propagates omnidirectionally, while a constant phase velocity is automatically guaranteed, enabling the formation of a uniform wavefront with a large beam aperture. Although similar phase-reconstruction effects were discussed for phononic graphene, none reported observing or taking advantage of the similar effect in microwave/photonic graphene. The challenge lies in the bulk edges where evanescent Bloch states emerge and interfere with the desired propagating Bloch state. We find that by adopting valley-constrained photonic topological insulator (PTI) protected borders and PTI waveguide, the proper modes are preserved, and we are able to experimentally observe the uniform wavefront generated in an all-dielectric microwave graphene bulk within a few wavelengths. This practically provides a possibility of developing low-profile devices with high directivity such as PTI horns or lenses.