Compression of high-intensity femtosecond laser pulses due to ionization self-phase modulation in gas-filled capillary tubes

We demonstrate experimentally the technique of high-intensity femtosecond laser pulse compression due to ionization-induced phase modulation in gas-filled dielectric capillary tubes for the first time. In our experiment, a laser pulse with an energy of 5 mJ and a duration of 85 fs (FWHM) at a wavelength of 0.792 mum was passed through a glass capillary tube 100 mum in diameter and 20 cm in length filled with Ar under a pressure of 1 torr. The spatial distribution of the output radiation was close to the fundamental mode. Starting from a 85-fs, 5-mJ laser pulse, we obtain a 35-fs, 2.3-mJ output pulse after compression by a 3-cm-thick silica plate. Our experimental result is in good qualitative agreement with our previously published numerical simulations for ionization dynamics of high-intensity femtosecond laser pulses in a gas-filled capillary.