fig1

Figure 1. (A) Crystal structures of stoichiometric LiNbO₃; (B) Congruent LiNbO₃ with $$ \mathrm{Nb}_{\mathrm{Li}}^{4+} $$ antisite defects and $$ \mathrm{V}_{\mathrm{Li}}^{-} $$ vacancies; (C) Nonlinear optical effect^[53]; (D) electro-optic effect^[53]; (E) piezoelectric effect^[53]; (F) waveguide structures^[53]; (G) transmittance curve^[53]; and (H) periodically poled LiNbO₃^[53]. Reproduced from Ref.^[53] with permission from the Journal of Synthetic Crystals. SHG: Second-harmonic generation; FH: fundamental harmonic; LN: LiNbO₃; LiNbO₃: lithium niobate.