Design and characterization of a quadrilayer magneto-optic disk

The use of quadrilayer film structures can maximize the magnetooptic (MO) effect in reflected light used for readout in optical data storage. A computer program and a multifilm optical model have been utilized to search for optimized quadrilayer structures based on various figures of merit (FOMs), including differential MO signal, shot-noise-limited SNR, and SNR expressions arising from other noise sources. Selection among various FOMs allows tradeoffs relative to the magnitude of the reflectance or thermal efficiency in writing. Disks were fabricated on the basis of the simulation design rules, and experiments were conducted to assess the recording performance. The authors report on the optimization search used in the design program and the formation of the associated FOMs, and they present data on signal and noise to illustrate the value of the model