The modern field of nonvolatile digital information storage is a bit more than a half-century old. During its history, the field has seen a small handful of technologies (magnetic tape, magnetic hard disk, magnetic flexible disk, consumer-derived optical disk) take root as ‘mainstream’. These technologies have persisted in the market place from their earliest introduction until today, experiencing commercial success for several decades or longer. A few other digital storage technologies have emerged and been successfully commercialized in less broad based applications (e.g. magnetic drums, optical cards, magneto-optical disk) and, typically, their success has been of shorter duration. A third, quite numerous, category of storage technologies involves new approaches that have not yet achieved commercial success. The subject of this book, holographic data storage, is in this third category.

Among the many examples of promising storage technologies that have been worked on over the past 50 years, holographic storage offers a unique combination of desirable attributes: extremely high density of stored information, a disk format capable of rapid random access, and a removable nonvolatile storage medium that may be inexpensively manufactured. While these attributes are simple to discuss in general, putting them all together in a practical and reliable storage system represents a herculean engineering task. This is exactly what InPhase Technologies has accomplished, and what the company’s contributors describe in detail in this book.

As the authors point out in the Introduction, with other optical storage technologies facing obstacles to significant performance improvements, interest in holographic data storage has dramatically increased in recent years. Although the increased interest is recent, the history of research and development in holographic storage extends back nearly 50 years, with contributions from many universities, government- and industry-sponsored consortia, and industrial companies. The uniqueness of the InPhase contribution is that they have progressed far beyond the basic research aspects of holographic storage and have persevered to address the multitude of materials, optical, mechanical and electrical engineering challenges necessary to develop a fully integrated drive-media storage system.

This book takes the reader through many details of the technical challenges encountered along this development path and of the often creative design solutions implemented to meet those challenges. Undoubtedly, the complexities of implementing a fully practical commercial system proved greater than anticipated by the InPhase teamat the outset, but that is a natural occurrence when attempting to break new ground and introduce a new technology that represents so significant a departure from the incumbent approaches. To the team’s credit, their approach over the years has been very open and forthcoming in describing the difficult challenges in their technical conference and journal papers. The team continues that practice in the detailed chapters of this book. Because of this openness, the book can serve as an excellent reference to developers of future holographic data storage systems and enable them to build upon and improve the technology.