Regular Paper

[OPTICAL REVIEW Vol. 21, No. 5 (2014) 551-555]
© 2014 The Japan Society of Applied Physics

Permanent Data Recording in Transparent Materials by Using a Nanojoule-Class Pulse Laser

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®


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