The thermal refractive index coefficients of 7.5 mol % Nb : KTiOPO4 crystals

The principal refractive indices and thermal refractive index coefficients for Nb:KTiOPO4 (KTP) crystal grown by the top-seed flux method from a start ing material containing 7.5 mol % Nb have been measured using the autocolli mation method. Using measurements made at wavelengths of 0.53975, 0.6328, 1 .0795, and 1.3414 mu m, in the temperature range from ambient to 188 degree s C, it is possible to determine the constants of the Sellmeier equations a nd the thermal refractive index coefficients as a function of wavelength. A lso, the temperature acceptance bandwidth at 90 degrees second harmonic gen eration noncritical phase matching direction was calculated. Comparison of these results with those for undoped KTiOPO4 [K. Rato, IEEE J. Quantum Elec tron QE-28, 1974 (1992)] and KNbO3 [B. Zysset, I. Biaggo, and P. Gunter, J. Opt. Soc. Am. B 9, 380 (1992)] implies that Nb-doped KTP crystals are suit able for blue coherent light devices. (C) 1999 American Institute of Physic s. [S0021- 8979(99)08019-6].