Energy scaling beyond the gas ionization threshold with divided-pulse nonlinear compression.

We demonstrate how pulse energy in hollow-core fiber can be scaled beyond gas-ionization limitations using divided-pulse nonlinear compression. With one pulse, ionization limits our fiber's output pulse energy to 2.7 mJ at an input of 4 mJ. By dividing the pulse to four low-energy pulses before the fiber, we eliminated the ionization and scaled the pulse energy 2.5× to 6.6 mJ at an input energy of 10 mJ. Larger energy scaling is possible, as our maximum pulse energy has not reached the new gas ionization threshold. Our results motivate applying the method to state-of-the-art systems for large pulse energy scaling without prohibitive system size increases.