Femtosecond Optical Parametric Amplification using β-BaB2O4 and BiB3O6 consecutively

We present a femtosecond Optical Parametric Amplificator (OPA) which was conceived to perform surgical interventions on eyes using eye-safe wavelengths. It is pumped by a Ti: sapphire laser. An OPA scheme using consecutively beta-BaB₂O₄ (BBO) crystal and BiB₃O₆ (BiBO) provides the required behaviour. For the first stage, a type I BBO is used because of it angular phase-matching selectivity. In the second stage, a type I BiBO allows a very good gain from 1.2 to 2.7 mum, while having identical angular phase-matching properties for all these wavelengths. Type I crystals are used as the pump polarisation and signal polarisation are perpendicular which allows to separate them easily. In our case, only nonlinear parametric effects are used which has a small compression effect. Consequently, the signal remains as long as the pump and a compressor is not needed. To summarise, the signal properties are : 50 fs pulse length, 1 kHz repetition rate and more than 150 muJ pulse energy, which correspond to an efficiency of almost 20 %.