Digital data are ubiquitous in modern life, and the capabilities of current storage technologies are continually being challenged by applications such as the distribution of content, digital video, interactive multimedia, small personal data-storage devices, archiving of valuable digital assets, and downloading over high-speed networks. Current optical data-storage technologies, such as the compact disk (CD), digital versatile disk (DVD), and Blu-ray disk (BD) have been widely adopted because they provide random access to data, are inexpensive removable media, and rapidly replicate video and music content.