Absolute non-linear optical coefficients of β BaB2O4crystals measurement by Second Harmonic Generation

We report here a characterisation of non-linear single β BaB2O4(BBO) crystals by Second Harmonic Generation (SHG). Due to high damage thresholds and a wide transparency range, BBO is one of most widely used crystals in non-linear optical devices. In spite of the great number of publications on this subject, the magnitude of the non-linear optical coefficients in BBO is still the subject of controversy. We propose room temperature absolute measurements of the effective non-linearity, deff, for type I and type II phase matched BBO crystals, with an accuracy estimated to be better than 10%. The d22 and d31 coefficients are deduced. The variation of the frequency conversion efficiency is measured as function of the deviation from the phase- matching direction. The angular bandwidths are deduced from these experimental data and interpreted.