Filamentation of femtosecond Gaussian pulses with close-to-linear or -circular elliptical polarisation

A numerical investigation was made of the formation and development of filaments in the propagation of high-power femtosecond Gaussian laser pulses in argon, whose polarisation is close to the linear or circular one. Filaments produced by close-to-circularly polarised pulses were found to be more uniform, greater in diameter, and higher in intensity than the filaments produced by close-to-linearly polarised pulses. For incident pulses with a close-to-linear (circular) polarisation, the degree of ellipticity of the radiation on the axis of the resultant filament becomes equal to zero (unity) at the instant of the peak of the local intensity.