Replication Data for: Electrically Pumped Topological Laser with Valley Edge Modes

Quantum cascade lasers (QCLs) are compact electrically-pumped light sources in the technologically important mid-infrared and terahertz (THz) region of the electromagnetic spectrum. Recently, the concept of topology has migrated from condensed matter physics into photonics, giving rise to a new type of lasing utilising topologically-protected photonic modes that can efficiently bypass corners and defects. Previous demonstrations of topological lasers have required an external laser source for optical pumping, and operated in the conventional optical frequency regime. Here, we report on the first demonstration of an electrically-pumped THz QCL based on topologically-protected valley edge states. Unlike previous topological lasers that relied on large-scale features to impart topological protection, we employ a compact valley photonic crystal design analogous to two-dimensional (2D) gapped valleytronic materials. Lasing with regularly-spaced emission peaks occurs in a sharp-cornered triangular cavity, even with the introduction of perturbations, due to the existence of topologically-protected valley edge states that circulate around the cavity without experiencing localisation. The properties of the topological lasing modes are probed by adding different outcouplers to the topological cavity. This is the first laser based on valley edge states and opens the door to practical use of topological protection in electrically-driven laser sources.