Phase transformations between amorphous and crystallized states are induced by irradiation with a single nanosecond laser pulse in Ge2Sb2Te5 films grown by pulsed laser deposition. By adjusting the laser fluence, the two different phases are obtained and can be distinguished by their different optical reflectivity. The effect of laser fluence on the crystalline nature of the films is studied in detail. Large structural differences between the laser-irradiated and thermally annealed films are revealed, due to the high heating rate and short duration of the laser pulse. X-ray reflectivity measurements show a density increase of 3.58% upon laser-induced crystallization.