Theoretical calculations and predictions of the nonlinear optical coefficients of borate crystals

Theoretical methods to calculate the optical response of crystals are reviewed. The second-harmonic generation coefficients of borate nonlinear optical crystals are calculated using the anionic group theory combined with the Gaussian'92 ab initio calculation method. Without adjusting the parameters, the calculated values are in good agreement with the experimental values. Meanwhile, a plane-wave pseudopotential total energy package is also used to calculate and discuss the theoretical background and accuracy of the theory. The results indicate that the anionic group theory can predict and calculate the nonlinear optical coefficients of borate crystals reliably, and the energy band calculations can reveal the relationship between nonlinear optical effects and microstructure.