Generation of sub-10-fs, 5-mJ-optical pulses using a hollow fiber with a pressure gradient

We propose and demonstrate a pulse compression technique using a hollow fiber with a pressure gradient. This technique improves the spatial and spectral qualities of femtosecond laser pulses spectrally broadened by self-phase modulation, and allows an increase of the pulse energy for pulse compression. Using chirped mirrors for dispersion compensation, we have successfully compressed the pulse to less than 10 fs with an energy as high as 5 mJ.