Propagation Of High-intensity Laser Pulses Research Articles

Comment on “Features of propagation of high-intensity laser pulses in Magnesium and Sodium fluoride crystals” by L. Bryukvina, Journal of Luminescence, 162 (2015) 145–148

The commented article contains numerous errors. The presentation of experimental data is slipshod and biased. They are not credible. The author had no reason to write about the scientific achievements outlined in the sections Abstract and Conclusion. One of the main conclusions of the work, that the author for the first time experimentally observed relation between orbital angular momentum of femtosecond laser radiation and induced by this radiation helicity of the tracks in crystals, has not been confirmed by direct check experiments. No orbital angular momentum of the exciting radiation nor the twisted tracks has been observed in the experiments. Other conclusions are also baseless.

Reply to the comment on “Features of propagation of high-intensity laser pulses in magnesium and sodium fluoride crystals”

Reply to the comment on “Features of propagation of high-intensity laser pulses in magnesium and sodium fluoride crystals”

Simulated laser-pulse evolution for high-order harmonic generation in a semi-infinite gas cell

We numerically simulate the propagation of high-intensity laser pulses in helium to investigate the role of nonlinear effects in gas-cell high-harmonics experiments. An aperture located before the focusing lens is also included in the simulation. Numerical results for the radial fluence profile as a function of axial position, as well as for the spectral shift and ionization levels, agree with experimental observations. The simulations confirm that a significant Kerr effect is not required to generate the observed double focus in the fluence. The beam simulation also permits an investigation of high-harmonic phase matching. Most of the harmonic energy is seen to come from the forward portion of the laser pulse, whereas the latter portion gives rise to the incidental double laser focusing. Good phase matching for the harmonics arises in large measure from a balance between the linear phase delay of the neutral atoms and the Gouy shift, which is elongated and nearly linearized when the aperture is partially closed on the beam.

Quasi-soliton and multifocal propagation of high-intensity laser pulses in silica glass

The results of numerical simulation of propagation of high-intensity ultrashort pulses in silica glass are presented. It is shown that in the case of a dynamic balance between self-focusing and defocusing induced by ionisation, radiation propagating in the glass over the distance of the order of a diffraction length can be captured to form a quasi-soliton. For certain relations between the parameters of radiation and glass over lengths exceeding the diffraction length, the multifocal propagation regime is possible.

Transparency of an overdense plasma layer.

The transition from opacity to transparency of overdense plasma layers for the propagation of high-intensity laser pulses of circular polarization is investigated theoretically and by simulation. We discuss in detail the regions where stationary solutions exist and therefore the plasma layer is opaque. We find that the opacity depends not only on the electron density and the laser intensity but also on the thickness of the plasma layer. We also discuss the overlap region where both transparency and opacity are possible and how it depends on the history. Ion acceleration is studied in both the opacity region and the transparency region.

Simulations of the propagation of high-intensity laser pulses in discharge-ablated capillary waveguides

We present the results of simulations of the propagation of high-intensity laser pulses in discharge-ablated capillary waveguides. The limitations of this type of waveguide for pulse intensities of the order of 1016 W cm-2 are discussed. However, for higher intensities we describe a new regime of quasi-matched guiding, that results in significant improvements in guiding performance. The effect on quasi-matched guiding of changing the atomic numbers of the atoms that compose the plasma waveguide is discussed. Calculations are presented for boron capillaries that show quasi-matched guiding over lengths of 32 mm for an input intensity of 5×1017 W cm-2.