Coherent combination of spectrally broadened femtosecond pulses for nonlinear compression

The coherent combination of ultrashort pulses has recently been established as a technique to overcome the limitations of laser amplifiers regarding pulse peak-power, pulse energy, and average power. Similar limitations also occur in nonlinear compression setups. In a proof-of-principle experiment, we show that the techniques developed for the combination of amplifiers can be adapted to nonlinear compression. We create two spatially separated pulse replica that undergo self-phase modulation in independent optical fibers and are recombined afterwards. Using this technique we demonstrate operation above the self-focusing threshold of a single pulse. Furthermore, we prove that the recombined pulses can be temporally compressed. This experiment paves the way for higher energy or average power operation of various nonlinear compression setups.