Simultaneous Multi-Bit Recording in Fused Silica for Permanent Storage

In recent years, optical discs and hard disc drives have been widely used as storage media. However, the lifetime of recorded data in these media is about 100 years. On the other hand, a permanent storage system that can store data for more than 1,000 years is strongly required, especially for historically valuable data. One candidate system for permanent storage is a system using fused silica, which is thermally and chemically stable. In this paper, we reported simultaneous multi-bit recording in fused silica with a femtosecond laser and a spatial light modulator. The recording quality was evaluated using signal-to-noise ratio with an optical microscope. We recorded a four-layer sample with a dot pitch of 2.8 mu m and obtained a signal-to-noise ratio greater than 15 dB. Furthermore, we confirmed that the sample had good thermal resistance at 1,000 degrees C for 120 min, which indicates a lifetime of over 319 million years. (c) 2013 The Japan Society of Applied Physics