ABSTRACT
Novel materials, devices, and systems are required for much faster data pro cessing, much higher recording density, and more specific and efficient sensing. Ultrafast switching materials that work in less than one picosecond (ps) are essential for THz communication. Several attempts have been reported for this purpose, which include optical switching by tunneling biquantum well semicon ductors or organic nonlinear optical materials [1]. Magnetic “hard” disks and heat-mode optical disks such as phase change or magneto-optical memories have rapidly been increasing their recording density owing to the development of new pickup heads or blue semiconductor lasers. But there is a physical limit in such “plane-type” memories to record data on the surface or in the thin surface layer of recording materials.
