Holographic and Volumetric Optical Data Storage: Physical Foundations, Materials, and Prospects for Sustainable Digital Archiving

The exponential growth of global data generated by cloudservices, artificial intelligence, and scientific research poses severe challenges toconventional magnetic and semiconductor storage media regarding recordingdensity, long-term durability, and power consumption. This review provides acomprehensive analysis of holographic and three-dimensional optical datastorage technologies as prospective candidates for long-term cold archives. Thephysical principles of volume interference, spatial multiplexing, and page-wisereadout are examined alongside the material properties of photopolymers,photorefractive crystals, and plasmonic metasurfaces. Special emphasis isplaced on digital processing techniques, including balanced modulation codes,phase retrieval algorithms, and deep learning-assisted decoding models.Furthermore, the paper analyzes industrial initiatives such as Microsoft's ProjectHSD and Project Silica, contextualizing their energy-efficiency benefits andstructural integration into modern data center tiered storage architectures.