Holographic Information Storage System: Today and Future

Holographic information storage systems using Collinear Technologies is proposed by Optware Corporation, Yokohama, Kanagawa, Japan, and in which the information and reference beams are modulated coaxially by the same spatial light modulator (SLM). With this unique configuration, the optical pickup can be designed as small as the DVDs and can be placed on one side of the recording disk. In a Holographic Versatile Disc (HVD) structure, the preformatted metadata reflective layer is used for the focus/tracking servo and reading address information, and the dichroic mirror layer is used for detecting holographic recording information without interfering with the preformatted information. A two-dimensional (2-D) digital page data format is used, and the shift-multiplexing method is employed to increased recording density of HVD. Experimental and theoretical studies suggest that the holographic material is very effective to increased recording density of the system. As the servo technology is being introduced to control the objective lens to be maintained precisely to the disk in the recording and the reconstructing process, a vibration isolator is no longer necessary. HVD will be compatible with existing disk storage systems, like CD and DVD, and enable us to expand its applications into other optical information storage systems