Dispersion-engineered multi-pass cell for single-stage post-compression of an ytterbium laser.

Post-compression methods for ultrafast laser pulses typically face challenging limitations, including saturation effects and temporal pulse breakup, when large compression factors and broad bandwidths are targeted. To overcome these limitations, we exploit direct dispersion control in a gas-filled multi-pass cell, enabling, for the first time to the best of our knowledge, single-stage post-compression of 150 fs pulses and up to 250 µJ pulse energy from an ytterbium (Yb) fiber laser down to sub-20 fs. Dispersion-engineered dielectric cavity mirrors are used to achieve nonlinear spectral broadening dominated by self-phase modulation over large compression factors and bandwidths at 98% throughput. Our method opens a route toward single-stage post-compression of Yb lasers into the few-cycle regime.

Multipass spectral broadening and compression in the green spectral range.

Multipass spectral broadening and compression around 515 nm are experimentally demonstrated. A nonlinear multipass cell with a bulk medium is used to compress 250-fs pulses down to 38 fs. The same input pulses create a sufficient bandwidth for sub-20-fs pulse generation in a multipass cell with gaseous media. In both cases, the efficiency exceeds 85%. Dispersion management by reduction of the cell size and the thickness of the nonlinear medium allows an efficient generation of ultrashort pulses in the visible range and establishes a pathway for ultraviolet spectral broadening by means of multipass cells.

60 fs, 1030†nm FEL pump-probe laser based on a multi-pass post-compressed Yb:YAG source.

This paper reports on nonlinear spectral broadening of 1.1 ps pulses in a gas-filled multi-pass cell to generate sub-100 fs optical pulses at 1030 nm and 515 nm at pulse energies of 0.8 mJ and 225 µJ, respectively, for pump-probe experiments at the free-electron laser FLASH. Combining a 100 kHz Yb:YAG laser with 180 W in-burst average power and a post-compression platform enables reaching simultaneously high average powers and short pulse durations for high-repetition-rate FEL pump-probe experiments.

Postcompression of picosecond pulses into the few-cycle regime.

In this work, we demonstrate postcompression of 1.2 ps laser pulses to 13 fs via gas-based multipass spectral broadening. Our results yield a single-stage compression factor of about 40 at 200 W in-burst average power and a total compression factor >90 at reduced power. The employed scheme represents a route toward compact few-cycle sources driven by industrial-grade Yb:YAG lasers at high average power.