Controllable finite ultra-narrow quality-factor peak in a perturbed Dirac-cone band structure of a photonic-crystal slab

We show that by using a perturbed photonic Dirac-cone, one can realize ultra-narrow and finite Q-factor peak in the wavevector space, with both value width separately tunable. also discuss lower bound minimal viable given Q-value while maintaining sufficient Q differentiation among modes. The strong angular frequency Q-selection finds applications optical devices where angle- frequency-selection is needed.