Ultrafast dynamics in strong-field interactions with molecules and solid surfaces: high-harmonic generation and nanostructuring

Abstract

This paper describes two topics of our recent studies on ultrafast strong-field interactions with atoms, molecules and solid surfaces. One is concerned with the high-order harmonic generation (HHG) from molecules nonadiabatically aligned with intense femtosecond (fs) laser pulses in a pump and probe experiment. The HHG is very sensitive to the molecular orbital and its spatial orientation with respect to the laser polarization. Experimental and theoretical studies demonstrate the characteristic properties of HHG from coherently rotating molecules. The other topic is the periodic nanostructure formation observed in fs laser ablation of dielectric materials. The major interest is in the ultrafast interaction process of nanostructuring on solid surfaces, for the purposes of potential applications of fs lasers to nanoprocessing. The experimental results have shown that enhanced near-field initiates the ablation of surface area much smaller than the laser wavelength and the origin of nanoscale periodicity can be attributed to the excitation of surface plasmon polaritons in the surface layer.