Robust and Efficient Temporal Pulse Combining Enabling Practical Coherent Pulse Stacking Amplification Systems

Practical use of laser plasma accelerators will require drivers with high peak power and high repetition rate. Spatially and temporally coherently combined fiber laser arrays offer one of the most promising pathways to such drivers. Temporal combining of ^~100 stretched pulses, implemented as a coherent pulse stacking amplification (CPSA) technique [1], enables near-complete extraction of stored energy in each fiber channel with low nonlinear phase per pulse, and reduces fiber-array size approximately by 100-fold as necessary for making this approach practical. However, stacking a large number of pulses robustly and efficiently is a challenging technical problem. In this paper, we report achieving highly stable 81-pulse temporal combining with efficiency larger than 83%. Theoretical analysis for system stability and alignment accuracy is carried out. High-precision alignment methods are developed theoretically and experimentally enabling to achieve the reported high fidelity system performance. This work shows the practicality of the CPSA technique as the key enabler of high energy and power LPA drivers.