Numerical simulations of the nonlinear propagation of femtosecond optical pulses in gases

Abstract

International audienceA two-dimensional axisymmetric model of the propagation of intense femtosecond laser pulses through dispersion-free transparent media is described. The effects of diffraction, nonlinear Kerr effect (instantaneous and retarded) and multiphoton ionisation are included. Numerical results concerning air and other gases are discussed. In particular, time self-compression of femtosecond pulses is predicted. Stable self-guided pulses are simulated, in agreement with recent experimental observations

Femtosecond Filamentation in Air

“…By moving the probe pulse perpendicularly to the propagation axis of the filament, the dimension of the object which modifies the refraction index (filament) is obtained, about 80 µm in the initial stage of the filamentation. This measurement is in agreement with numerical results [10,20,47]. Yang et al [92] measured the phase contrast and obtained similar results.…”

Systematic study of spatiotemporal dynamics of intense femtosecond laser pulses in BK-7 glass

“…The present study concentrates on spatio-temporal dynamics, i.e., the dynamics of the spatial profile and the temporal envelope. The studies of Kumagai et al [21], Couairon et al [25] and Chiron et al [22] justify retaining only the transverse Laplacian in the space-time focusing term for longer pulse widths, 100 fs or longer, when it is of interest to study only the spatio-temporal dynamics for pulses which are not in the few cycle limit. For the same reason we can ignore third-order GVD, self-steepening and Raman response.…”

“…The NLS equation in this form has been successfully used to explain nonlinear effects in various media, notably in optical fibers [23]. This limited form of the equation does not adequately explain the observed spectral broadening [6][7][8][9] and spatiotemporal dynamics [16][17][18][19][20][21][22] accompanying the propagation of intense laser pulses above the critical power for self-focusing. In addition, for powers above P cr , self-focusing leads to a spatial collapse of the beam into a singularity, which is unphysical.…”

“…Thirdly, we examine the role of GVD in channel formation and bring to light the insignificant role of diffraction in multiple-cone formation due to the early onset of a sufficiently strong plasma. Another highlight of this paper, as is the case with some others [22], is that the NLS equation is solved numerically using a commercially available personal computer. Many groups use multinode computing machines to solve the NLS equation or Maxwell's equations directly, to study the propagation of ultrashort pulses for more general cases.…”

Ultrafast light-matter interaction in transparent medium

“…This necessitates a complete understanding of the physical processes that govern the spatio-temporal dynamics of the intense ultra-short pulse in the medium. The theoretical description of laser-induced refractive index changes in the interaction of high-intensity laser pulses with plasma was considered by many authors [12][13][14][15]. The spontaneous breakup of highly elliptical laser beams into one-and two-dimensional arrays of light filaments was studied in fused silica [16], where the multiple filamentation process is initiated by random intensity modulation across the beam "amplitude noise".…”