Application of optical-field-ionization-induced spectral broadening in helium gas to the postcompression of high-energy femtosecond laser pulses

International audience; We report a detailed numerical study on the postcompression of high-energy (∼30 mJ) femtosecond laser pulses (∼40 fs), using the spectral broadening induced by optical-field ionization of a low-pressure helium gas in a capillary. Our numerical results are in very good agreement with previously published experimental data on spectral shapes, transmitted energies and recompressed pulse durations in the full range of laser energies and gas pressures investigated. Then, we calculate the performances of the method with shorter input pulses (∼20 fs) and demonstrate that few optical cycles recompressed pulses with 5 to 8.5 mJ energy could then be achieved.