Structural and optical characterization of beta barium borate thin films grown by electron beam evaporation

Abstract

Thin films of beta barium borate (β-BBO) were deposited by electron beam physical vapor deposition on MgO(100) substrates. The deposition conditions were optimized so that the thin films would grow preferentially in a c-axis orientation. At a deposition temperature of 650°C, thin films grown on a MgO(100) substrate were found to be highly textured, with (00l) orientation (c-axis) normal to their surface. The addition of 4mol % of TiO2 to the BaO–B2O3 system stabilized the β-BBO crystalline phase without inducing significant variations in the optical properties of the thin films with respect to those of β-BBO bulk single crystal. The film crystallized in situ at 650°C exhibited a maximum effective second harmonic generation coefficient, deff, of 1.85pm∕V, which is comparable to the d22 coefficient of bulk β-BBO crystal.