One-way valley-locked waveguide with a large channel achieved by all-dielectric photonic crystals

One-way transmission of light constitutes the cornerstone of modern photonic circuits. In the realm of photonic devices, it has been widely utilized in isolators, circulators, etc. Recent topology in artificial materials, an unprecedented degree of freedom, has been proposed to solve the effect of impurities on one-way transmission. However, in view of the bulk-edge correspondence, the spatial width of the transmission channel with uniform field distribution is quite narrow and needs further exploration. In this paper, we proposed a one-way valley-locked waveguide with a large channel in an all-dielectric reciprocal photonic crystal. Quite different from the topological edge states, our waveguide is topologically trivial; the unidirectional property comes from the bulk modes with valley-lock in the vicinity of Dirac points, which can naturally fully utilize the whole dimension of the structure. Additionally, such one-way bulk modes keep single mode regardless of the channel width increasing, along with uniform electrical field distribution across the entire channel, which opens a new avenue for large channel optical devices.