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R&D: High-Speed Reference-Beam-Angle Control Technique for Holographic Memory Drive

Could enable Gb/s transfer rate.

Japanese Journal of Applied Physics has published an article written by Ken-ichiro Yamada, Takeshi Ogata, Makoto Hosaka, Koji Fujita, Center for Technology Innovation – Information and Telecommunications, Hitachi, Ltd., Yokohama 244-0817, Japan, and Atsushi Okuyama, Department of Precision Engineering, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan

Schematic view of optical system during reproduction.

IS15018fig01_hr

Abstract: “We developed a holographic memory drive for next-generation optical memory. In this study, we present the key technology for achieving a high-speed transfer rate for reproduction, that is, a high-speed control technique for the reference beam angle. In reproduction in a holographic memory drive, there is the issue that the optimum reference beam angle during reproduction varies owing to distortion of the medium. The distortion is caused by, for example, temperature variation, beam irradiation, and moisture absorption. Therefore, a reference-beam-angle control technique to position the reference beam at the optimum angle is crucial. We developed a new optical system that generates an angle-error-signal to detect the optimum reference beam angle. To achieve the high-speed control technique using the new optical system, we developed a new control technique called adaptive final-state control (AFSC) that adds a second control input to the first one derived from conventional final-state control (FSC) at the time of angle-error-signal detection. We established an actual experimental system employing AFSC to achieve moving control between each page (Page Seek) within 300µs. In sequential multiple Page Seeks, we were able to realize positioning to the optimum angles of the reference beam that maximize the diffracted beam intensity. We expect that applying the new control technique to the holographic memory drive will enable a gigabit/s-class transfer rate.»

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