Nonradiative bound states in the continuum (BICs) have emerged as a powerful paradigm for subwavelength field localization and boosted light–matter interactions. However, conventional BICs sustain ultrahigh Q-factors only within an extremely narrow spectral window. Here, we introduce lattice perturbations into moiré photonic crystal slabs and realize ultrahigh-Q BICs simultaneously over broad wavelength and wavevector ranges via lattice-perturbation-induced Brillouin zone folding.
