Evaluation of Hologram Multiplexing Method for High-Density Recording

The holographic information recording provides ultra-high density and fast read/write by using storage media in three-dimension. We developed the hologram multiplexing evaluation system to achieve ultra-high density recording. In this study, we investigated two methods of hologram optics, two-beam optics and collinear one. The two-beam optics gave a recording density of about 2.6 Mbit/mm², however, this value is not enough for ultra-high density recording. This is because of the diffraction limit of objective lens induced by optical configuration. However, the collinear optics does not have the structural limitation because the optics of signal beam and reference beam is in co-axial. Furthermore, to increase the recording density we developed the method of the dynamic reference pattern recording. As the results, the recording density of 430 Mbit/mm² was obtained, which corresponds to the recording capacity of 0.5 TByte for a disc with size of 12 cm.