Enhanced Third-Harmonic Generation in Diamond Photonic Crystal Slabs via Doubly Resonant Quasi-Bound States in the Continuum
Researchers engineered a diamond photonic crystal slab to achieve doubly resonant third-harmonic generation by simultaneously matching the fundamental and third harmonic modes within the same structure. By breaking symmetry using triangular holes, they enabled a previously forbidden nonlinear coupling, leading to high efficiency ($2.7 imes10^{-7}~ ext{W}^{-2}$) and establishing a scalable route for on-chip frequency conversion in all-diamond platforms.