Premastered Optical Disk by Superresolution

Premastered optical disk by superresolution (PSR) for practical use has been achieved for the first time. The PSR disk has a phase-change material Ge2Sb2Te5 with stoichiometric composition. Superresolution results from a high contrast ratio of reflectance in the light spot between highly reflective crystal region and lowly reflective melted region. A high C/N ratio of 56 dB is obtained at a pit length of 0.4 µm using PSR. The C/N ratio is still as high as 50 dB for a pit length of 0.3 µm. The PSR disk with double linear densities of current CD is successfully read out with a clear eye pattern and a low error rate using current optics.