Enhancement of temporal contrast in a femtosecond petawatt Ti:sapphire laser

Significant enhancement of temporal contrast is achieved in a femtosecond petawatt Ti:sapphire laser. A pulse cleaning technique, combining double-CPA, non-collinear optical parametrical amplification and second harmonics generation, is applied to improve the amplified spontaneous emission (ASE) contrast. Meanwhile, pre-pulse leaking from the regenerative amplifier is suppressed by double Pockels cells and a saturable absorber. Measurement results show that pre-pulse on nanosecond scale can be effectively suppressed and the ASE contrast can be improved from the original ∼10^-8 to ∼2 × 10^-12. Proton acceleration experimental results with a foil target also demonstrate a significant enhancement of temporal contrast.