Holography and optical storage

Abstract

The term holography is composed of the Greek words holos (= whole) and graphein (= to record, to write), and thus summarizes the key aspects of its underlying principle: recording the complete wavefront of an object, i.e., its intensity as well as its phase. Interference and diffraction phenomena are employed to record and retrieve the full information, a technique pioneered by Dennis Gabor in 1948. He was honored with the Nobel prize in Physics in 1971, reflecting the general impact of holography on modern physics. Holography plays an essential role in today's science and industry. Relevant applications making use of its principle have been developed, including three-dimensional (3-D) displays and holographic cameras, interferometers for nondestructive material analysis, archival data storage systems, diffractive optical systems, and embossed display holograms for security features. The success of holography was made possible in particular by the availability of coherent laser-light sources. In the meantime holography has even been performed using microwaves, neutrons, electrons, x-rays, and acoustic waves. The first part of this chapter is dedicated to holography itself. It provides an introduction to the historical development and reviews the principle of wavefront reconstruction. This section also includes an overview of hologram classification, recording/read-out geometries, holographic techniques and recording materials. Special emphasis is given to explaining the principles of some of the most important holographic applications, finishing with a brief insight into a few of the latest discoveries making use of Gabor's principle, such as holographic scattering and neutron diffractive optics. The second part of this chapter addresses trends in optical data storage optical storage, focussing on holographic data storage. It highlights different approaches to achieving increased optical storage density. This section also discusses the historical development of optical storage, the need for increased storage densities (and hence storage capacities) and the role of optical storage systems in today's life. Various approaches to increasing the areal density of optical storage systems are introduced. Next, the advantages of and approaches to volume optical recording that are currently under consideration for future generations of optical storage systems are presented. The state of the art as well as physical and technical attempts to realize holographic data storage are discussed in detail. © Springer-Verlag Berlin Heidelberg 2012.