Absolute non-linear optical coefficients of beta BaB2O4 crystals measurement by second harmonic generation

We report here a characterisation of non-linear single beta BaB2O4(BBO) cry stals by Second Harmonic Generation (SHG). Due to high damage thresholds an d 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 cont roversy. We propose room temperature absolute measurements of the effective non-line arity, d(eff). for type I and type II phase marched BBO crystals, with an a ccuracy estimated to be better than 10%. The d(22) and d(31)coefficients ar e deduced. The variation of the frequency conversion efficiency is measured as functio n of the deviation from the phase- matching direction. The angular bandwidt hs are deduced from these experimental data and interpreted.