2019 Volume 88 Issue 10 Pages 653-658
Combining the conventional concept of “congruent” with the essentially new concept of “stoichiometry”; a material with the activities of its constituent elements being unity is stoichiometric, we have developed cs-MgO:LiNbO3 and cs-MgO:LiTaO3 by introducing Mg and a vacancy, both of which are simultaneously congruent and stoichiometric. They yield no segregation of ionic species during growth so that there is no compositional change in the growing crystals even if they experience an unexpected perturbation, which is not possible with the conventional congruent LiNbO3 (c-LiNbO3). They are easy to grow with an extremely homogeneous composition and are effective at achieving excellent nonlinear optical properties. The growth fundamentals are thermodynamically and experimentally explained.