A proposed beam-addressable memory

The feasibility of optical beam-operated magnetic storage systems is assessed. Recent advances in laser technology and in transparent magnetic materials are described along with methods for writing and reading information. In the writing process, thermomagnetic recording on thin films is considered and the writing speed and resolution is calculated, illustrating the large performance improvement obtainable compared with existing magnetic recording techniques. The progress in materials, beyond the previously used metals, has developed towards more transparent magnetic media while retaining large intrinsic magneto-optical rotation. Consequently, large signal-to-noise ratios are obtained which relax the material uniformity requirements. The properties of ferrites, garnets, and rare-earth compounds are compared with metals to illustrate this advance. At the present time, technical problems exist with a light beam in achieving random access to a large field. This limitation is alleviated, however, in certain types of memories where the access requirements combine sequential and random motions. As an example, a prototype memory is discussed for a computer input-output system having certain performance advantages. In this memory, sequential access is achieved with a rotating mirror and random access by means of a digital light-deflector.