Ultrafast Excitation and Dynamics Measurements with Intense Ultrashort Laser Pulses —High-Order Harmonic Generation from Aligning Molecules and Surface Nanostructuring—

Abstract

This paper reviews our recent studies on ultrafast, strong-ˆeld interactions with atoms, molecules and solid surfaces. The major in- terest in atomic and molecular processes is concerned with nonperturbative nonlinear processes induced with intense ultrashort laser pulses, especially, high-order harmonic generation from nonadiabatically aligned molecules and its dynamics measurements. Ex- perimental and theoretical results demonstrate characteristic properties of the harmonic generation from coherently rotating mole- cules, depending on molecular structures. Concerning the interaction with solid surfaces, the periodic nanostructure formation observed in femtosecond laser ablation of thinlm surfaces has been the subject for the purpose of potential applications of ultrashort laser pulses to nanoprocessing. It is found that the nano-scale ablation is initiated with laser-induced near-ˆeld on solid surfaces, and the nano-periodicity is attributed to the excitation of surface plasmon polaritons. The results obtained show that the intense ultrashort- pulse laser is a promising tool for investigating new and/or latent dynamics and functions of matter.