Control of compression dynamics by spatially adjustable femtosecond filamentation

The influence of spatial laser field distribution on the formation of femtosecond filaments in Ar and on the consequent pulse compression was investigated. Beams with increased symmetry demonstrate more efficient energy coupling in the filament supporting development of negative spectral chirp and producing broader spectra with a clear expressed shift on shorter wavelengths side. It is found, that modification of the spatial beam profile performs fine control of compression dynamics resulting in phase adjustment of the output pulses approaching optimum for a given experimental configuration. As a demonstration the pulses with initial duration of 45 fs was compressed down to 8.2 fs with 0.9 mJ energy by means of spatially adjustable filamentation