Temporal optimization of ultrabroadband high-energy OPCPA

We present general guidelines for the design of ultrabroadband, high-energy optical parametric chirped-pulse amplifiers, where maximization of both conversion efficiency and bandwidth and simultaneous suppression of superfluorescence is required. Using a semi-analytical approach together with numerical simulations, we find that the ratio of pump and seed pulse durations is a critical parameter in temporal optimization, and its optimum depends on the amplifier gain. Multi-stage amplifier design thus requires independent optimization of seed chirp at each amplification stage. We find that a small compromise in amplifier bandwidth relative to the full phase-matching bandwidth, through use of the appropriate seed chirp, both maximizes the efficiency-bandwidth product and optimizes the signal-to-noise ratio. On the other hand, maximization of signal bandwidth is found to significantly degrade both the signal-to-noise ratio and the conversion efficiency.