The crater morphology upon femtosecond laser ablation from BaF2 and CaF2, exhibits several periodic structures of characteristics that cannot be explained by interference phenomena. More likely, the ripple pattern presents features of self-organization from a chaotic state. The ablation under the applied conditions is due to Coulomb explosion of the surface, which indicates that local thermal effects should play a minor role in the ripple formation. In this paper, we present morphological structures that point toward instabilities and self-organization. (C) 2002 Elsevier Science B.V. All rights reserved.