Dynamic Response of Reflectivity of Metal/GeS2 Systems during Laser Irradiation in Nanosecond Range.

We constructed an equipment for measuring rapid changes in reflectivity of optical recording materials on test pieces during recording laser irradiation, which is very important in a development of these kinds of materials, with a time resolution less than 10 ns. Using this equipment, we examined the metal/GeS2 systems in the performance as recording materials for Write Once Read Many (WORM) optical disks. Seven kinds of metals were tested. Differences in the profiles of the reflectivity changes during the laser irradiation were clearly elucidated depending on the metal layer materials. In/GeS2 and Sn-Bi/GeS2 (Sn-Bi:Sn-57wt%Bi eutectic alloy) samples showed the most rapid decreases in the reflectivity with low laser power absorbed in the samples. These results suggest that In/GeS2 and Sn-Bi/GeS2 are promising for the WORM optical recording material with high sensitivity and high recording speed.