A numerical study of self-focusing and guiding of laser pulse of duration shorter than plasma wavelength

Abstract: Self-focusing and guiding of ultra-short (pulse duration: L<lambda_P: plasma wavelength), intense laser pulses in underdense plasma relevant to laser wakefield electron acceleration has been studied numerically. The analysis considers contribution of wakefield non-linearities along with relativistic effects. Stable propagation of laser pulse with mild periodic oscillations upto few Rayleigh lengths were observed. Parametric optimization of the different laser and plasma parameters performed show that, laser pulse as short as L/lambda_P~0.42 is most stably guided upto few Rayleigh lengths for normalized laser intensity, a0~0.9. Next effect of upward density ramps were also studied and it was found that inclusion of an upward density ramp not only enhances self-focusing and guiding of the ultra-short laser pulse but also reduces required minimum laser intensity compared to uniform density profile.