Topological Lasing from Thouless Pumping in Bilayer Photonic Crystal.

Topological lasing leverages concepts from topological physics to achieve single-mode light amplification within topological bandgaps, offering robustness against fabrication imperfections. Recent advances in microelectromechanical systems (MEMSs) and phase-change materials (PCMs) at the subwavelength scale promise new avenues for dynamically reconfigurable topological lasers, enabling robust and tunable nanoscale light sources. Here, we numerically demonstrate a dynamically reconfigurable lasing action at telecom wavelengths in a bilayer photonic crystal through the mechanisms of Thouless pumping. By designing two competing periodic potentialsone slowly translating photonic grating atop another stationary onewe observe a transition between a topological pumping regime and conventional mode oscillation. A carefully engineered heterojunction between these phases supports a robust lasing mode that can be dynamically tuned via MEMSs or reversible PCMs. Our work establishes bilayer photonic crystals as a programmable platform for achieving topological light sources, showcasing a potential pathway for merging topological photonics with reconfigurable photonic devices.