Laser-induced periodic surface damage and radiation remnants

We report a detailed experimental study of the periodic surface damage induced by laser irradiation at 1.06 μm on nominally smooth Ge samples; we include novel observations of the damage obtained by studying its optical diffraction pattern, which reveals a previously unappreciated richness in the damage structure. The usual ’’surface scattered wave’’ explanation of the damage is criticized; we argue that the damage results from the electromagnetic fields generated by surface inhomogeneities but that, due to the presence of the interface between vacuum and bulk Ge, these fields are not radiative; these ’’radiation remnants’’ are discussed.