Holographic recording media and devices

This article is divided into four main sections: an introduction to the vocabulary used in holography, and three sections that classifies the holographic recording media into permanent materials, refreshable media, and electronic devices. The first section defines the terminology frequently used in holography such as the difference between phase, amplitude, or surface relief grating; transmission or reflection holograms; as well as the Raman-Nath or Bragg regimes of diffraction. This section also contains a definition of the different figures of merit characterizing the holographic recording materials: sensitivity, spectral sensitivity, efficiency, spatial resolution, stability, scattering, absorption spectrum, thickness shrinkage, and reciprocity. The second section discusses the most conventional recording materials which are the ones where the hologram is recorded permanently. These materials are historically the first to have been widely used, and are still very important in commercial applications such as security tags, artwork, and holographic optical elements. They are also used to develop holographic sensors. The third section is describing the materials where the hologram can be refreshed, either by an external process, or by simply re-illuminating the device. These materials have been investigated by researchers for their potential use in data storage, 3D display, and dynamic light interaction such as beam coupling, phase conjugation, and imaging through turbid media. Finally, the fourth section presents the electronic devices that support either the recording of an interference pattern, or the dynamic display of diffraction structures. Considering their refresh rate, ease of use, and constant improvement in term of space-bandwidth product, these devices are taking a more and more important role in the research and development of dynamic systems relying on diffraction optics. Electronic devices certainly represent the future of active holography.