Influence of the deuteration level of the KD⁎P crystal on multi-PW class OPCPA laser

The deuteration level of the KD⁎P crystal plays a key role in the performance of large aperture OPCPA amplification stages. Whilst purely deuterated crystals show broadband amplification around 910 nm, the availability and optical quality of that type of crystal limit its use. A lower deuteration level has an impact on the phase matching and will increase the absorption in the IR region, reducing the bandwidth and the efficiency. However, these crystals have better optical quality and are easier to grow. In this paper we present a numerical study of OPCPA amplification for different deuteration levels, looking in particular at the small signal gain bandwidth and absorption. This study is important for the design and the realization of multi-PW laser systems based on OPCPA techniques.