Phase-Matching of Optically Second-Harmonic Generation in the Single Crystals of Gd- and La-Added Barium Sodium Niobate

Optically microscopic observation, measurements of the phase-matching temperature of second-harmonic generation (SHG) and evaluation of the SHG conversion efficiency were carried out for three kinds of single crystals: barium sodium niobate (BNN), La-added BNN [BN(La)N] and Gd-added BNN [BN(Gd)N]. The best crystalline-quality crystal was [BN(Gd)N] and the crystal showing the highest SHG conversion efficiency was also [BN(Gd)N]. The phase-matching temperatures were about 120°C and 160°C. Some discussion was given on the SHG phase-matching.