Numerical calculation of the effective second-order nonlinear coefficient along collinear phase-matching directions inside nonlinear crystals in three-wave interaction

In this work, we present the first numerically calculated values of the second-order nonlinear coefficient D_eff along collinear phase-matching directions inside the biaxial crystal. We have demonstrated our results using KTP in optical parametric generation. Our results are in agreement with recent experimental data. The theoretical approach presented here is a simple and generalized method which encompasses H. Ito´s and B. Wyncke´s works