Simultaneous localization of photons and phonons within the transparency bands of LiNbO₃ phoxonic quasicrystals.

We report the properties of dual phononic-photonic band gaps and localized modes of eightfold lithium niobate (LiNbO₃) phoxonic quasicrystals (PhXQCs). Complete and large phoxonic band gaps are easily achieved despite the low refractive index of LiNbO₃ substrate. Point defect intentionally introduced can form localized modes within both forbidden and transparency bands over a wide range of geometric parameters. Further analysis indicates that the localized modes within transparency bands originate from the intrinsic high-order rotational symmetry of quasiperiodic structures, which resemble whispering gallery modes. LiNbO₃ PhXQCs provide a good candidate to enhance phononic-photonic interaction and show considerable advantage over the periodic counterparts.