부산대학교 도서관

Graphene, with its massless Dirac surface states, exhibits large THz nonlinear susceptibilities leading to efficient THz high harmonic generation (HHG). However, the THz HHG efficiency in graphene strongly saturates with increasing incident field strength, limiting the HHG field conversion efficiency to a level of 1%. Here, we show that the THz HHG efficiency can be significantly enhanced at high THz driving fields by mitigating the overheating problem, making use of the efficient heat exchange between surface and bulk states of topological insulators. By implementing topological-based metamaterials for field enhancement, THz third harmonic generation with $\sim 10$% field conversion efficiency is demonstrated. These results are of particular interest for efficient on-chip optoelectronic devices operating at ultrahigh frequencies.