Second harmonic generation phase-matching locus for 7.5 mol% Nb:KTP crystals at near-infrared wavelengths

Both the type-II second harmonic generation (SHG) phase-matching locus in the three principal planes of 7.5 mol% Nb:KTiOPO/sub 4/ (KTP) crystals for wavelengths less than 1.8 /spl mu/m and the type-II SHG phase-matching locus for 7.5 mol% Nb:KTP crystals for wavelengths of 970, 980, 1064.2, and 1311.4 nm are calculated on the basis of the Sellmeier equations. When compared with those in KTP crystals, the shapes of these curves are almost the same in the two crystals. These imply that Nb doping does not significantly change the phase-matching properties of KTP crystals, even though it does largely change the phase-matching parameter of KTP crystals. These make Nb:KTP crystals more attractive in direct SHG of semiconductor laser radiation to produce blue coherent light.