Angle-dependent x-ray emission and resonance absorption in a laser-produced plasma generated by a high intensity ultrashort pulse

Abstract

Plasmas were generated by 400 fs KrF laser pulses at intensities of ~~10 17 Wcm -2 on aluminum targets. Reflectivity and x-ray emission were measured as a function of laser polarization, angle of incidence, and intensity. For the same absorbed intensity, p-polarized laser light is up to a factor of 5 more efficient in generating x rays ( > 0.5 keV) than s-polarized light. These results show the importance of an additional absorption process, besides collisional absorption, for short scale length plasmas that is effective for /^-polarized light only and has the characteristics of resonance absorption.

Three-halves harmonic emission from femtosecond laser produced plasmas

“…Such plasmas are sources of strong x-ray and particle emission with energies of up to several 10 MeV. In addition to resonance absorption 3,4 parametric plasma instabilities contribute to the generation of suprathermal electrons and also lead to the generation of large amplitude plasma waves which couple to the incident electromagnetic wave and result in new, frequency-shifted electromagnetic emission. An example of such a process is the generation of light with a frequency of 3/2 times the fundamental frequency.…”

Polarization dependent micro-structuring of silicon with a femtosecond laser

“…Resonance absorption in plasma was shown to depend on the angle of incidence and often the differences in absorption between s and p polarization were found to be maximum for an angle of incidence in the 35-45 • range. However, for normal incidence, as is the case in the present experiment, the absorption remained the same for both polarizations [2,4,46,47] and is unlikely to play a role.…”

Production d'impulsions ultracourtes de rayons X par interaction laser matière

“…L'utilisation d'une onde laser en polarisation p et en incidence oblique [19,[21][22][23], dont une composante du champ électrique est normale à la cible, favorise la conversion de l'énergie laser en électrons suprathermiques. Sur le plan théorique, deux mécanismes ont été identifiés.…”