Ryo IMAI¹, Manabu SHIOZAWA¹, Takao WATANABE¹, Mariko UMEDA¹, Toshiyuki MINE¹, Satoshi KURETAKE², and Koichi WATANABE¹

¹Central Research Laboratory, Hitachi, Ltd., Kokubunji, Tokyo 185-8601, Japan
²Murata Manufacturing Co., Ltd., Nagaokakyo, Kyoto 617-8555, Japan

(Received November 28, 2013; Accepted May 15, 2014)

We investigated data recording for permanent data storage using an ultrafast pulse laser with nanojoule-class pulse energy and megahertz-class repetition rate in transparent materials, and driveless reading based on a simple imaging system. A transparent ceramics called Lumicera^®, manufactured by Murata Mfg. Co., Ltd., was used as the recording medium. Lumicera^® has a lower modification threshold and a higher recording sensitivity than those of silica glass, namely, the medium previously studied. Structural modification in Lumicera^® occurs by light exposure for 10 μs, suggesting that Lumicera^® has potential for a recording speed of over 100 kbps. Data recorded in Lumicera^® resists heating for 2 h at 1000 ℃ and is expected to have a lifetime of over 300 million years. Moreover, the data recorded in Lumicera^® was successfully read with a reading system based on a smart phone.

Key words: femtosecond laser, silica glass, optical memory, optical storage, archive, Lumicera^®