Cubic optical nonlinearity of KTiOPO4

We perform angular non-critical phase-matching third-harmonic generation (T HG) experiments in KTiOPO4 (KTP). From these experiments, we determine the magnitude and sign of the two phase-matched nonlinear coefficients of KTiOP O4 by a complete analysis of phase-matching properties of the cascaded quad ratic and pure cubic processes. the resolution of the coupled propagation e quations and by the calculation of the quadratic and cubic dielectric susce ptibility tensor by an extended bond charge model; we find: chi(24)((3))(53 9 nm) = 14.6 x 10(-22) m(2) V-2 and chi(16)((3)) (491 nm) = 8.0 x 10(-22) m (2) V-2. We also demonstrate that the two studied THG are mainly governed b y the cubic interaction.