The scenario of the formation of light bullets in the presence of anomalous group velocity dispersion is presented within the same general scenario for condensed matter and humid air. The temporal and spectral parameters of light bullets during filamentation in fused silica and humid air are obtained. A light bullet (LB) is a short-lived formation in a femtosecond filament with a high spatiotemporal light field localization. The sequence formation of the quasi-periodical LB is obtained numerically and is confirmed experimentally by autocorrelation measurements of the LB’s duration. The estimation of the LB duration reaches few-cycle value. It is established that the generation of each LB is accompanied by the ejection of a supercontinuum (SC) in the visible spectrum and an isolated anti-Stokes wing is formed in the visible area of the SC as a result of destructive interference of broadband spectral components. It was found that the energy of a visible SC increases discretely according to the number of LBs in the filament. We demonstrated that the model of ionization in solid dielectric which is used in numerical simulation fundamentally affects the obtained scenario of LB formation. The possibility of the formation of LBs under the filamentation of middle-IR pulses in the atmosphere was shown with numerical simulation.

The formation of light bullets during femtosecond laser pulse filamentation in the presence of anomalous group velocity dispersion has been recorded for the first time. The minimum experimentally detected width of the light bullet autocorrelation function is 27 fs, which corresponds to a duration of about 13.5 fs. The duration of the light bullet at a wavelength of 1800 nm is about two periods of the light field oscillation. The numerically calculated width of the autocorrelation function for such a light bullet is 23 fs, which is in good agreement with the experimental value.

International audienceThe formation of silver cluster structures at submicrometer spatial scales under the irradiation by high-power femtosecond laser pulses with high repetition rate was observed in various glasses containing silver ions. In order to account for the formation of these structures in metal-doped glasses, we present a theoretical model for the organization of noble metallic clusters induced by a train of femtosecond laser pulses. The model includes photoionization and laser heating of the sample, diffusion, kinetic reactions, and dissociation of metallic species. This model was applied to reproduce the formation of cluster structures in silver-doped phosphate glass. The parameters of the silver structures were obtained numerically under various incident pulse intensities and number of pulses. Numerical modeling shows that the involved microscopic physical and chemical processes naturally lead to the emergence of a silver cluster organization, together with charge migration and subsequent trapping giving rise to a strong static electric field buried in the irradiated area as experimentally observed. Based on this modeling, a theoretical basis is provided for the design of new metallic cluster structures with nanoscale size

We have demonstrated that in the IR pulse filament the anomalous dispersion of fused silica leads to the formation of an isolated anti-Stokes wing (ASW), which is located in the visible region of the supercontinuum (SC). It is shown that the isolated ASW is formed by the interference of the light field of a SC undergoing anomalous group velocity dispersion.

For the first time, lasing at NV− centers in an optically pumped diamond sample is achieved. A nanosecond train of 150-ps 532-nm laser pulses was used to pump the sample. The lasing pulses have central wavelength at 720 nm with a spectrum width of 20 nm, 1-ns duration and total energy around 10 nJ. In a pump-probe scheme, we investigate lasing conditions and gain saturation due to NV− ionization and NV0 concentration growth under high-power laser pulse pumping of diamond crystal.

Structured solid targets are widely investigated to increase the energy absorption of high-power laser pulses so as to achieve efficient ion acceleration. Here we report the first experimental study of the maximum energy of proton beams accelerated from sub-micrometric foils perforated with holes of nanometric size. By showing the lack of energy enhancement in comparison to standard flat foils, our results suggest that the high contrast routinely achieved with a double plasma mirror does not prevent damaging of the nanostructures prior to the main interaction. Particle-in-cell simulations support that even a short scale length plasma, formed in the last hundreds of femtoseconds before the peak of an ultrashort laser pulse, fills the holes and hinders enhanced electron heating. Our findings reinforce the need for improved laser contrast, as well as for accurate control and diagnostics of on-target plasma formation.

Single-molecule magnets in hybrid architectures with plasmonic nanoantennas exhibit significant enhancement in their magneto-optical response.

No abstract