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We perform numerical simulations to investigate the nonlinear propagation dynamics of femtosecond Gaussian and vortex beams in fused silica. By analyzing the extent of spectral broadening, we are able to distinguish between the linear, self-focusing, and filamentation regimes. Additionally, the maximum intensity and fluence distribution within the cross-section of the vortex beams are analyzed for different incident laser energies. The results demonstrate a direct correlation between the spectral broadening and the peak intensity of the femtosecond laser pulse. As a result, this provides a theoretical foundation for distinguishing different propagation regimes, and determining critical powers for self-focusing and filamentation of both femtosecond Gaussian and structured beams. [ABSTRACT FROM AUTHOR]

The filamentation of femtosecond pulses has attracted significant attention, owing to its unique characteristics and related applications. The self-focusing critical power of femtosecond pulses is one of the key parameters in the filamentation process and its application. However, the experimental determination of this power remains a challenging task. In this study, we propose an experimental approach to investigating the critical power for self-focusing of both femtosecond Gaussian and vortex beams with relatively low topological charges by analyzing the changes in the focal spot at different propagation distances. Our work offers a practical and convenient method for determining the self-focusing critical power of femtosecond pulses. [ABSTRACT FROM AUTHOR]

We report an experimental study on the behaviour of femtosecond Gaussian and vortex laser pulses during filamentation in turbulent water. The transverse and longitudinal wandering, intensity, and spectral broadening of the filamentation are evaluated. The results show that the filamentation of femtosecond vortex pulses is less affected by water turbulence than that of Gaussian pulses. Furthermore, the filamentation is less affected when the turbulence is located close or within the filamentation region, in contrast to the self-focusing region. These findings highlight the potential benefits of using femtosecond vortex pulse filaments in liquid-based applications. [ABSTRACT FROM AUTHOR]

• Filamentation of femtosecond vortex pulse is shown to be less influenced by air turbulence than that of Gaussian pulse. • Pointing stability, longitudinal wandering, intensity and spectral broadening of filamentation are experimentally studied. • The turbulence introduced in the self-focusing regime will significantly increase the deviations of the filamentation. • The higher resistance of the filamentation of vortex pulses to air turbulence will facilitate long-distance applications. We experimentally investigate the performance of the filamentation of femtosecond vortex laser pulses in turbulent air. The pointing stability, longitudinal wandering, and intensity of filamentation, as well as spectral broadening are evaluated by compared with the case of femtosecond Gaussian laser pulses. The results show that filamentation of femtosecond vortex pulse is less influenced by air turbulence than that of Gaussian pulse. All the characteristics of filamentation of vortex laser pulses, including the transverse pointing, longitudinal position, intensity, and the spectrum, are more stable even if the turbulence is introduced in the self-focusing regime, which is helpful to long-distance applications of the filamentation of femtosecond vortex pulses in the atmosphere. [ABSTRACT FROM AUTHOR]