An amorphous to a polycrystal or a single‐crystal transition by ruby‐laser irradiation of amorphous Si, obtained through ion implantation, is discussed. Both free‐generation andQ‐switched laser mode operation are used. Under a free‐generation operation only the amorphous to polycrystal transition is obtained, which is attributed to nonthermal effects. In theQ‐switched mode both transitions are obtained. The single‐crystal transition is interpreted as due mainly to the melting of the amorphous layer.