Absolute non-linear optical coefficients of β BaB₂O₄ crystals measurement by Second Harmonic Generation

Abstract

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, d_eff, 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.

Key Words:

• Non-linear crystal
• frequency conversion
• Borates