Modeling magneto-optical thin film media for optical data storage☆

Abstract Magneto-optical (MO) thin film systems are extensively studied as potential media for erasable storage of digital data by optical means. While writing of data is accomplished by thermo-magnetic processes, reading is done by sensing the change of polarization on reflection by the polar Kerr magneto-optic effect. The polar Kerr effect itself is quite small, normally being a fraction of a degree in rotation of polarization, and hence multilayer interference schemes have been studied to enhance the polar Kerr rotation in order to improve the signal-to-noise ratio in the readback process. We discuss a scheme and a computer code based on it, to determine all the relevant optical responses, such as reflectance, transmittance, Kerr rotation, ellipticity etc., for a general multilayer incorporating one or more magneto-optical films. The scheme can handle magnetic and optical anisotropies of arbitrary orientations in any of the films in the multilayer. Some of the key problems in the design of the media, such as birefringence in the substrate, and stress and growth-induced problems in the films, can be studied.