Manipulation for one-way large-area helical waveguide states in topological heterostructure

Photonic topological insulators (PTIs) have been extensively attracting attention recently because of unique characteristics in manipulating electromagnetic waves. In this work, we construct a kind of heterostructure consisting of a domain of nontrivial topological photonic crystals (TPCs) sandwiched between two domains of trivial TPCs by using all-dielectric materials, systematically analyze and discuss projected photonic bulk bands structures with 3, 5, 6 layers nontrivial TPCs in heterostructures, and theoretically achieve one-way large-area helical topological waveguide states with pseudospin-polarized and robustness. Based on intrinsic chirality of helical edge states, we calculate the chirality map of one-way large-area topological waveguide states by quantifying Stokes parameters. Furthermore, we realize a series of specific manipulation for one-way large-area topological waveguide states, for example, we achieve interesting waveguide functionalities with valley-splitting and four-channel of one-way large-area topological waveguide states in a topological heterostructure with a cross-like route based on chirality map. We realize a wavelength division multiplexing in specific topological heterostructure based on distributions of dispersion curves of topological waveguide states in different heterostructures. The work provide a new promising and valid guideline for practical design and applications in multi-function integrated photonic devices, such as high-capacity energy transport, field enhancement.