LiNbO3 linear and nonlinear optical response from first-principles calculations

The dielectric function and second harmonic generation of ferroelectric LiNbO₃ is calculated from first-principles. Thereby we start from the electronic structure calculated within the density functional theory. The use of the GW approach to account for quasiparticle effects and the subsequent solution of the Bethe-Salpeter equation leads to a dielectric function that is in excellent agreement with the available experimental results. Our second harmonic generation calculations rest on the independent particle approximation and predict strong non-linear coefficients, in particular in the energy range starting from 1.5 eV.