1D quasi-bound states in the continuum with large operation bandwidth in the <i>ω</i>∼<i>k</i> space for nonlinear optical applications

The phenomenon of bound state in the continuum (BIC) with infinite quality factor and lifetime has emerged recent years photonics as a new tool manipulating light-matter interactions. However, most investigated structures only support BIC resonances at very few discrete points w~k space. Even when is switched to quasi-BIC(QBIC) resonance through perturbation, its frequency will still be located within narrow spectral band close that original BIC, restricting their applications many fields where random or multiple input frequencies beyond are required. In this work, we demonstrate set QBIC can supported by making use special binary grating consisting two alternatingly aligned ridge arrays same period zero-approaching width difference on slab waveguide. These distributed continuously over broad along line space thus considered one-dimensional QBICs. With Q factors generally affected difference, it now possible choose arbitrarily any dispersion achieve significantly enhanced interactions, facilitating wavelengths required, e.g. sum generations nonlinear optics.