The amorphous silicon film, excited by a picosecond laser, has been investigated by a laser microprobe. The optical properties are measured simultaneously with its Raman spectrum. The sharp Raman peak of this properly annealed film is similar to that of crystalline silicon (c-Si) with a significant drop in reflection. A second pulse of proper fluence can reduce the Raman intensity and increase the transmission greatly and this is ascribed to explosive crystallisation and laser quenching. This reamorphisation phenomenon of the annealed film suggests a feasible method for erasable optical recording.