Highly accurate servo control of reference beam angle in holographic memory with polarized servo beam

Hosaka, Makoto; Ogata, Taiki; Yamada, Kazutoyo; Yamazaki, Kazuyoshi; Shimada, Kunio

doi:10.7567/jjap.55.09sa03

Cited by 4 publications

(2 citation statements)

References 39 publications

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“…Until now, to suppress the Bragg mismatch, tolerance analysis 16,17) and several servo control methods for maintaining the Bragg matching condition have been proposed. [18][19][20] By applying these methods to the HDSS, the effect of Bragg mismatch on the intensity profile can be minimized.…”

Section: Introductionmentioning

confidence: 99%

Reduction of intensity gradient in two-dimensional holographic data page

Shimada

Hosaka

Yamazaki

et al. 2018

Jpn. J. Appl. Phys.

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The data transfer rate as well as recording data density of holographic data storage systems can be further improved by utilizing a high-numericalaperture (NA) objective lens. Meanwhile, a high-NA lens is likely to develop an inhomogeneous intensity profile of a holographic data page. In our previous experiment employing an objective lens with NA of 0.6, a steep intensity gradient was observed over an area of a reproduced data page; consequently, the quality of the data channel degraded. We introduce a readout scheme that maximizes a coupling constant; the constant was originally defined in the coupled wave theory. Owing to the readout scheme, the intensity gradient in the reproduced holographic data page was successfully reduced. In addition to the constant, we found that the angle dependences of the transmittance and reflectance of a holographic medium were also a factor for the development of the intensity gradient and should be suppressed to reduce the gradient further.

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Section: Introductionmentioning

confidence: 99%

Reduction of intensity gradient in two-dimensional holographic data page

Shimada

Hosaka

Yamazaki

et al. 2018

Jpn. J. Appl. Phys.

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“…By developing an optical architecture for generating angle error signals 10,11) and adaptive final-state control (AFSC), 12) we have successfully demonstrated the servo control of the reference beam angle with a settling time of less than 300 µs and an accuracy of a relative angle of less than ±3.0 mdeg between the recording and the readout state. [10][11][12] On the other hand, although several previous studies of the positioning of the holographic disc in a HDSS using angularly multiplexed recording have been reported, 13,14) an effective technique that satisfies both the highly precise and high-speed positioning of the holographic disc has not yet been proposed. One of the difficulties is the higher moment of inertia of the holographic disc than of the galvano mirror.…”

Section: Introductionmentioning

confidence: 99%

Technique for positioning hologram for balancing large data capacity with fast readout

Shimada¹,

Hosaka²,

Yamazaki³

et al. 2017

Jpn. J. Appl. Phys.

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The technical difficulty of balancing large data capacity with a high data transfer rate in holographic data storage systems (HDSSs) is significantly high because of tight tolerances for physical perturbation. From a system margin perspective in terabyte-class HDSSs, the positioning error of a holographic disc should be within about 10 µm to ensure high readout quality. Furthermore, fine control of the positioning should be accomplished within a time frame of about 10 ms for a high data transfer rate of the Gbps class, while a conventional method based on servo control of spindle or sled motors can rarely satisfy the requirement. In this study, a new compensation method for the effect of positioning error, which precisely controls the positioning of a Nyquist aperture instead of a holographic disc, has been developed. The method relaxes the markedly low positional tolerance of a holographic disc. Moreover, owing to the markedly light weight of the aperture, positioning control within the required time frame becomes feasible.

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