16 - 3D Data Storage and Near-Field Recording

Abstract

Optical memory devices are becoming essential items of audio and visual media as well as of external computer memory media. In these devices, a laser beam is used to record and read information. As the laser spot can be focused within a 1 μm scale, optical memory can thus access higher density and capacity than conventional magnetic memories. Photochromic materials are developed in order to increase the memory density. The chapter illustrates three-dimensional (3D) optical data storage and near-field recording techniques using photochromic materials for high-density memory. In 3D data storage, multilayered bit data are recorded in a 3D volume of photochromic materials. It is noted that the reversible transformation of the photochromic molecules between the two isomers with different absorption spectra can be stimulated by irradiation with light of appropriate wavelengths, thus allowing information to be stored. The chapter also presents optics for 3D memories using photochromic materials and demonstrates the near-field recording technique for high-density storage, and its application to near-field microscopy for biology.