Control of femtosecond filamentation by means of the alignment of gas molecules by short-wavelength infrared laser pulses

It has been demonstrated experimentally that both the single and multiple filamentation of a femtosecond laser pulse in gaseous nitrogen can be controlled by means of the nonadiabatic alignment of molecules by 1400-nm pulses. The spectral shifts and change in the duration of a pulse caused by changes in the refractive index in the revival regions of a rotational wave packet have been detected. The stable and reproducible localization of radiation into separate filaments with the subdiffraction divergence and broadening of the spectrum by more than an octave has been observed in the multiple filamentation regime upon the alignment of molecules in the direction perpendicular to the pulse polarization.