Intellectual Property

First Steps Taken Towards Practical Application of Holographic Memory

05 December 2017

In recent years, due to technology like the internet and 8K broadcasting, more information is being distributed across the world than ever before. With this trend, there is a demand for an innovative method for storing large volumes of data at ultra-high recording density and at ultra-high speed. Magnetic-holographic memory meets this demand. The new technology enables more than 1 TB worth of data, which is equivalent to the total capacity of 40 Blu-ray discs, to be recorded in a disc the size of a DVD or Blu-ray disc.

Reconstructed image with and without magnetic assist. Source: Toyohashi University of TechnologyReconstructed image with and without magnetic assist. Source: Toyohashi University of Technology

In magnetic hologram recording, a medium is magnetized in one direction, then the medium is irradiated with a signal beam and a reference beam, and the resulting interference pattern is recorded in the form of the difference in magnetization directions. When the recording proceeds with an external magnetic field applied to it, the recording of the difference in magnetization directions becomes clearer. The latter process is called magnetic assist recording.

The research group led by Yuichi Nakamura, associate professor at the Toyohashi University of Technology, has applied this magnetic assist recording technology to magnetic-holographic memory and succeeded in reducing recording energy consumption and achieving non-error data reconstruction.

Through simulation, the group investigated the size of the stray magnetic field required for magnetization reversal in magnetic hologram recording. As a result, they found that the thinner the medium, the smaller the necessary stray magnetic field and the less clear the hologram recording.

They also proved through experiments that magnetic assist recording yields a clear magnetic hologram even with a thin medium and the magnetic hologram yields a bright reconstruction beam upon irradiation with a reference beam.

Through further experiments, they found that magnetic assist recording and reconstruction of 2D data yields clear reconstruction images. As a result of this research, the group has enabled, for the first time, a significant reduction in errors in data recording and recording with a small amount of energy as well as non-error recording and reconstruction with magnetic-holographic memory.

"Until now it has been difficult to obtain a clear reconstruction image with a magnetic hologram, due to strict requirements for material characteristics, optical conditions, and so on. Using magnetic assist recording, we have relaxed these requirements and also improved the reconstruction performance of recording media. This technology is promising for the future application of magnetic-holographic memory," says first author Shirakashi.

The researchers intend to proceed with their work to improve recording density. Their goal is to apply this technology to make a portable, ultra-high-density, high-speed optical information storage medium capable of storing high-volume contents from various sources, including 8K Super Hi-Vision broadcasting and 3D films. They also want to enable wide application of this technology in various types of storage systems, including archive and cold storage for storing information like medical image data, SNS data on the internet and high-volume data in data centers.

The paper on this research was published in Scientific Reports.

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