Refractive indices, phase-matching directions and third order nonlinear coefficients of rutile TiO_2 from third harmonic generation

Experiments of third harmonic generation in rutile TiO2 allowed us to determine the phase-matching angles and the refractive indices of the crystal up to 4500 nm. We also showed that χ16 and χ18 coefficients of the third order electric susceptibility tensor exhibit opposite signs, and that |χ18(616.7nm)| = 9.7 × 10−20 m2V−2.