Linear and nonlinear optical susceptibilities in some ferroelectrics: Ab-initio calculation

We present a first principles calculations of the second-order optical response functions as well as the dielectrics function for ABO3 (A=K, Li, Ba; B=Ti, Ta, Nb) and A5B6C7 (A=Sb; B=S, Se; C=I, Br) ferroelectrics. Specially, we evaluate the dielectrics function ε(ω) = ε1(ω) - i ε2 (ω) and the second harmonic generation response coefficent χ(2) (-2ω, ω, ω, ω) over a large frequency range. The electronic linear electro-optic susceptibility χ(2) (-2ω, ω, ω, ω, 0) is also evaluated below band gap. These results are based on the series of self-consistent LDA calculations within DFT.