A structure change from a polycrystal to single‐crystal layer in ion‐implanted Si samples has been obtained by single‐pulse ruby‐laser irradiation with a power density threshold of about 70 MW cm−2(pulse length 50 nsec). Under these conditions surface mechanical damage is produced. A laser pulse train shaping technique was adopted to reduce the residual disorder in the layer after laser irradiation and to prevent mechanical damage.