The world's appetite for high-performance mass storage grows exponentially. Today's advanced computing systems are only marginally served by existing mass storage products, despite the remarkable advances in the 1980s of magnetic, optical, and semiconductor devices. Hence, great interest is focused on beam-addressable and wavelength or frequency-selectable optical memories that simultaneously provide very large capacities, fast random access, and very high I/O rates.Like never being too thin or too rich, one can never have enough storage. Over the years, a consistent refrain has been that the demand for storage would moderate and the capabilities of semiconductor and magnetic storage technologies would soon reach their limits. Yet during the past decade, demand for storage has had an average annual growth rate of over 30%; the price/performance of every type of memory has improved remarkably and is still doing so at a phenomenal pace.