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

We report the properties of dual phononic-photonic band gaps and localized modes of eightfold lithium niobate (LiNbO) phoxonic quasicrystals (PhXQCs). Complete and large phoxonic band gaps are easily achieved despite the low refractive index of LiNbO 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. LiNbO PhXQCs provide a good candidate to enhance phononic-photonic interaction and show considerable advantage over the periodic counterparts.