  Edge states protected by bulk topology of photonic crystals show robustness
against short-range disorder, making robust information transfer possible.
Here, topological photonic crystals under long-range deformations are
investigated. Vertices of each regular hexagon in a honeycomb crystalline
structure are shifted randomly to establish a deformed system. By increasing
the degree of random deformations, a transition from an ordered system to an
amorphous system are investigated, where the close of topological bandgap is
clearly shown. We further present comprehensive investigations into excitation
methods of the proposed deformed system. Due to the lack of strict periodicity,
excitation of topological edge modes becomes difficult. Chiral and linearly
polarized sources as two different methods are investigated respectively. It is
found that chiral sources are sensitive and rely on the ordered lattice. Even a
weak long-range deformation can bring fluctuations to transmission. We further
designed and fabricated metal-dielectric-metal sandwich-like samples working in
the microwave band. Using linearly polarized source, we detected the existence
of topological transport in the deformed system. This work investigates
excitation and robustness of bulk topology against long-range deformations and
may open the way for exploiting topological properties of materials with a
deformed lattice.
