Manifold coherent combining of few-cycle pulses in hollow-fiber compressors

We demonstrate fourfold coherent combining in a gas-filled hollow-fiber compressor with 92 % efficiency. Our passive approach relies on the use of carefully oriented birefringent plates for temporal pulse dividing and combining. We perform a detailed theoretical and experimental analysis of the effects degrading the combining process, as polarization change or nonlinear interactions between pulse replicas. We show how to overcome these limitations to generate 10-fs output pulses with high temporal quality.