Blueshifted continuum peaks from filamentation in the anomalous dispersion regime

Filamentation in the anomalous dispersion regime is experimentally shown to give rise to an extreme blueshifted continuum peak in the visible region even when the filament is formed by near-infrared pulses. Measurements and numerical simulations allow us to identify this peak as an axial component of the conical emission. Its features are characterized and quantitatively reproduced by the effective three-wave mixing model.

Figure 1

Supercontinuum measured at the center of the conical emission after filamentation in 3 cm of fused silica of a 1.9-μm, 35-fs pulse at different input energies. Inset: Photo of the conical emission at 15 μJ.

Figure 2

Spectra measured at the center of the conical emission after filamentation in a 4-cm-thick fused silica sample. The central wavelength used for filamentation ranged from 1.2 to 2.4 μm. The visible part of the spectra up to 1 μm is magnified by a factor of 10 for ${\lambda }_0$ (1.2–1.5 μm) and by a factor of 2 for ${\lambda }_0$ (1.6–2.4 μm).

Figure 3

(a) Computed pulse temporal evolution during filamentation in a 3-cm-long fused silica sample. The input pulse has central wavelength ${\lambda }_0=1.9$ μm, duration 70 fs, and energy 7.2 μJ. The black line marks the slope for calculating the velocity of the intensity peak. (b) ($\theta ,\lambda$) spectrum obtained by numerical simulation. The dashed curves show the fit with Eq. (2).

Figure 4

Angular distribution of the conical emission, after filamentation of 1.9-μm, 40-fs, 26-μJ pulses in 3 cm of fused silica. This figure has a logarithmic scale. The white curves show the fit with Eq. (2).

Figure 5

Calculated and measured visible component that is generated during filamentation in a 3-cm-thick fused silica sample as a function of the input pulse central wavelength.