LiNbO3 & MgO:LiNbO3 Crystals LiNbO3 crystal is a low cost photoelectric material with good mechanical and physical properties as well as high optical homogeneity. It has been widely used as frequency doublers for wavelength > 1mm and optical parametric oscillators (OPOs) pumped at 1064nm as well as quasi-phase-matched (QPM) devices.