Topological Insulator Laser Using Valley-Hall Photonic Crystals

Topological photonics has recently been proven as a robust framework for manipulating light. Active topological photonic systems, in particular, enable richer fundamental physics by employing nonlinear light-matter interactions, thereby opening a new landscape for applications such as topological lasing. Here we propose an all-dielectric topological insulator laser scheme in the telecommunication region based on semiconductor cavities formed by topologically distinct Kagome photonic crystals. Our theoretical results show that the proposed planar semiconductor Kagome lattice can lift degeneracy with geometrical perturbation and open broad photonic bandgaps, and valley-dependent edge states and topologically robust transport with subwavelength scale confinement are observed at the edge of the perturbed Kagome lattices with distinct valley Chern numbers. An interesting feature of the Kagome lattices is that it supports two different types of valley Hall edge modes, which enables the coexistence of high Q ring-resonator modes and lossy Fabry–Pérot resonator modes in the proposed topological cavities. Moreover, we explore pumping and lasing dynamics of the topological cavities by means of a four-level two-electron model and demonstrate that this model offers a powerful platform to investigate non-Hermitian topological laser cavities with arbitrary geometry. The proposed topological semiconductor scheme provides a new route to study non-Hermitian topological photonics and to develop integrated topological systems for robust light generation and transport.