Pump-seed synchronization for MHz repetition rate, high-power optical parametric chirped pulse amplification

We report on an active synchronization between two independent mode-locked lasers using a combined electronic-optical feedback. With this scheme, seed pulses at MHz repetition rate were amplified in a non-collinear optical parametric chirped pulse amplifier (OPCPA). The amplifier was seeded with stretched 1.5 nJ pulses from a femtosecond Ti:Sapphire oscillator, while pumped with the 1 ps, 2.9 µJ frequency-doubled output of an Yb:YAG thin-disk oscillator. The residual timing jitter between the two oscillators was suppressed to 120 fs (RMS), allowing for an efficient and broadband amplification at 11.5 MHz to a pulse energy of 700 nJ and an average power of 8 W. First compression experiment with 240 nJ amplified pulse energy resulted in a pulse duration of ~10 fs.