ABSTRACT
The pump laser pulse was assumed to be circularly polarized with a Gaussian temporal profile, a FWHM duration of 34 fs and a peak input intensity of 1 x 1018 Wcm"2. The incoming laser field was taken as a sum of several (typically 9) Gaussian propagating modes as the best fit of the experimentally measured fluence profile in several planes before and after the best focal plane in vacuum. In the case of propagation inside the capillary, a boundary layer with a dielectric constant larger than 1 was introduced to simulate the capillary wall. Its value was adjusted so as to reproduce the measured value of the transmitted pump energy which is about 40% at a pressure of 25 Torr, and -80% at 17 Torr.
