Seminarium Optyczne

The interaction between femtosecond laser pulses and plasma surfaces can lead to the generation of high-order harmonics. This mechanism provides an alternative to harmonic generation in gas targets and is especially interesting in the view of conversion efficiency.Since the laser pulse amplitude for laser-plasma interaction (typically above 1018 W/cm2) can vastly exceed the intensities used for atomic harmonics (up to 1014 W/cm2) the generated radiation can be far more intense. In the relativistic regime the harmonics intensity can even exceed the intensity of the focused laser pulse.Harmonic radiation generated from relativistic laser-plasma interaction can be used for nonlinear optics in the extreme ultraviolet regime (XUV) and the generation of atto-second radiation. On the other hand the details of the laser-plasma interaction influence the harmonics spectrum, i.e. details of the harmonic spectrum reveal information about the motion of the plasma surface, plasma waves, electron transport inside the plasma and large electric and magnetic fields at the surface.In the presentation the physics behind high-order harmonic generation in the relativistic regime of laser-plasma interaction will be presented. Prospective applications as coherent XUV sources are highlighted. The influence of plasma parameters such as surface density gradient scale-length and plasma temperature on the harmonics spectrum will be discussed.