Efficient Second Harmonic Generation in Coupled Dual Topological Dislocation States

Defects, as ubiquitous phenomena in materials science, manifest in various forms including line defects. Among these, dislocations—a typical line defect—exhibit topological dislocation states with special topological properties in topological insulators. Protected by the system's overall topological nature, these states demonstrate exceptional local characteristics and stability, thereby possessing significant potential in nonlinear optical processes. Experiments have confirmed that topological disclination states can efficiently generate second harmonics, demonstrating that the nonlinear optical response induced by topological defects has a solid physical foundation. This paper proposes a novel dual‐topological dislocation‐state coupling structure. By designing specific geometric configurations, it satisfies the fundamental requirements for efficient second‐harmonic generation. This approach not only significantly enhances energy conversion efficiency but also inherits the robust insensitivity to external perturbations characteristic of traditional topological insulators. This research further expands the theoretical framework for how topological defects influence nonlinear optical effects, offering new insights for exploring nonlinear light sources based on topological states.