During laser pulse irradiation, the
temperature increase in the rear part of the spot is higher than that in the front
part owing to the rotation of the disk. When the local temperature in the mask
layer exceeds the melting temperature, the layer changes from a solid to liquid
(melted) state
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