Because the reflectivity of the material at the melted state is often
the rear part of the laser spot can be effectively
masked by the phase-changed layer, which is equivalent to a spot size reduction.
In principle, the size of the aperture can be controlled by modulating the laser
intensity. When an aperture with a diameter smaller than the diffraction limit is
formed, marks smaller than the diffraction limit can be recorded/read out combined
with the near-field effect. The low optical throughput still seems to be a technical