The new XUV sources, which deliver spatially coherent pulses of high peak power, allow to study elementary processes in the light/solid interaction in the high intensity regime (⩾1011W/cm 2). Here, we report two studies which have used high-order laser harmonics (HH) generated in gas as the excitation source. Firstly, we have investigated the dynamics of electron relaxation in the wide gap CdWO 4 dielectric crystal, an efficient scintillator material, using time-resolved luminescence spectroscopy. The kinetics decay of luminescence shows evidence of non radiative relaxation of the self-trapped excitons at the μs damage to surfaces of poly(methyl methacrylate) - PMMA, induced by a multi-shot XUV-irradiation (1 kHz reprate) for given fluence, below damage threshold range of ≈mJ/cm 2. The main processes participating in the surface modification, polymer chain scission followed by the blow up of the volatile, molecular fragments and cross-linking in the near-surface layer of remaining material, are tentatively identified and associated to, crater formation for short-time exposure (< 1min ) and surface hardening for long-time exposure (⩾1min ).© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.