100-Layer recording in fused silica for semi permanent data storage

Data storage using fused silica is a candidate archival medium for long-term preservation of important data such as official documents and cultural heritages. It is highly resistant to high temperature and chemical damage, and the Arrhenius law suggests that it would have a semi permanent lifetime. In order to improve the recording density of this type of storage, we increased the number of recording layers to 100 and achieved a recording density of 1.5 Gbyte/in.2 without the use of an error correction code. The total bit error rate of all 100 layers was 2.3 × 10−4, which is acceptable for practical use. The analysis of the experimental results suggests that a further increase in the number of recording layers is possible by the correction of the spherical aberration induced by a mismatch in the refractive index at the surface of a medium.